CN110655922B - Using In 3+ Wavelength tuning of ZnSe quantum dots with salts as dopants - Google Patents

Abstract

The present invention relates to the field of nanotechnology. More specifically, the invention relates to highly luminescent nanostructures, in particular highly luminescent nanostructures comprising an indium-doped ZnSe core and a ZnS and/or ZnSe shell. The invention also relates to methods of producing such nanostructures.

Description

Wavelength tuning of ZnSe quantum dots using In3+ salt as dopant

Technical field

The present invention relates to the field of nanotechnology. More specifically, the present invention relates to highly luminescent nanostructures, in particular highly luminescent nanostructures comprising an indium-doped ZnSe core and a ZnS and/or ZnSe shell. The invention also relates to methods of producing such nanostructures.

Background technique

Semiconductor nanostructures can be incorporated into a variety of electronic and optical devices. The electrical and optical properties of such nanostructures vary, for example, depending on their composition, shape and size. For example, the size-tunable properties of semiconductor nanoparticles are of great interest for applications such as light-emitting diodes (LEDs), lasers, and biomedical labeling. Highly luminescent nanostructures are particularly ideal for this application.

To fully exploit the potential of nanostructures in applications such as LEDs and displays, nanostructures need to simultaneously meet five criteria: narrow and symmetric emission spectra, high photoluminescence (PL) quantum yields (QYs), high optical stability, and ecological Friendly materials and low-cost mass production methods. Most previous research on highly emissive and color-tunable quantum dots has focused on materials containing cadmium, mercury, or lead. Wang, A. et al., Nanoscale 7: 2951-2959 (2015). However, there are growing concerns that toxic substances such as cadmium, mercury or lead pose serious threats to human health and the environment. Furthermore, the European Union's Restriction of Hazardous Substances rules ban any consumer electronics containing more than trace amounts of these substances. Therefore, there is a need to produce materials that are free of cadmium, mercury and lead for the production of LEDs and displays.

There is significant interest in using colloidal nanocrystals as emitters in display architectures similar to existing organic light-emitting diodes (OLEDs), which are expensive to produce, have low yields due to the need for many high vacuum deposition equipment, and their emission wavelengths are only Can be changed by changing the emitting molecule. Quantum dot light-emitting diodes (QLEDs) offer the prospect of cheap production methods such as inkjet printing, as well as the ability to exploit quantum confinement effects to tune the emission wavelength by changing the size of the emitter particles. Currently, the highest-performing QLEDs use Cd (a substance that is currently restricted in Europe) and is likely to be restricted elsewhere.

ZnSe is an attractive material for blue electroluminescent quantum dots because no cadmium or other restricted materials are required. An important obstacle to the use of ZnSe in display applications is that pure ZnSe cannot be made with a wavelength long enough to achieve the required CIE coordinates, and the photoluminescence quantum yield is significantly compromised as the emission wavelength increases above 435 nm.

There is a need to prepare nanostructured compositions with peak wavelengths higher than 435 nm that do not sacrifice the high photoluminescence quantum yield of pure ZnSe quantum dots.

Contents of the invention

The present disclosure relates to a nanostructure comprising a core surrounded by at least one shell, wherein the core comprises ZnSe and indium dopants, wherein the at least one shell comprises ZnS, and wherein the nanostructure has an emission wavelength in the range of approximately Between 435nm and approximately 500nm.

In some embodiments, the nanostructures emit at a wavelength between 440 nm and 480 nm. In some embodiments, the nanostructures have emission wavelengths between 440 nm and 460 nm.

In some embodiments, the nanostructure includes a core surrounded by a shell.

In some embodiments, the nanostructure includes a core surrounded by at least one shell, wherein at least one shell contains 3 to 8 ZnS monolayers.

In some embodiments, the nanostructure includes a core surrounded by at least one shell, wherein at least one shell contains about 6 ZnS monolayers.

In some embodiments, the nanostructure further includes a buffer layer between the core and at least one shell. In some embodiments, the buffer layer includes ZnSe. In some embodiments, the buffer layer contains 2 to 6 ZnSe monolayers. In some embodiments, the buffer layer contains about 4 ZnSe monolayers.

In some embodiments, the nanostructures have a photoluminescence quantum yield of 50% to 90%. In some embodiments, the nanostructures have a photoluminescence quantum yield of 60% to 90%.

In some embodiments, the FWHM of the nanostructure is between about 10 nm and about 40 nm. In some embodiments, the nanostructures have a FWHM between about 10 nm and about 30 nm.

In some embodiments, the nanostructure includes a buffer layer containing 2 to 6 ZnSe monolayers and at least one shell containing 3 to 8 ZnS monolayers.

In some embodiments, the nanostructures are quantum dots.

In some embodiments, the nanostructures are cadmium-free.

In some embodiments, nanostructures are used in devices.

The present disclosure relates to a method of producing nanocrystal cores, comprising:

(a) mixing a source of selenium and at least one ligand to produce a reaction mixture; and

(b) contacting the reaction mixture obtained in (a) with a zinc source and at least one indium salt;

to provide a nanocrystal core containing ZnSe and indium dopants.

In some embodiments, the selenium source in (a) is selected from trioctylphosphine selenide, tris(n-butyl)phosphine selenide, tris(sec-butyl)phosphine selenide, tris(tert-butyl)phosphine selenide Phosphine, trimethylphosphine selenide, triphenylphosphine selenide, diphenylphosphine selenide, phenylphosphine selenide, cyclohexylphosphine selenide, octaselenol, dodeceselenol, selenol, elemental selenium, Hydrogen selenide, bis(trimethylsilyl)selenide and mixtures thereof. In some embodiments, the selenium source in (a) is trioctylphosphine selenide.

In some embodiments, at least one ligand in (a) is selected from trioctylphosphine oxide, trioctylphosphine, diphenylphosphine, triphenylphosphine oxide, and tributylphosphine oxide. In some embodiments, at least one ligand in (a) is trioctylphosphine.

In some embodiments, the zinc source in (b) is selected from diethyl zinc, dimethyl zinc, zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc carbonate , zinc cyanide, zinc nitrate, zinc oxide, zinc peroxide, zinc perchlorate and zinc sulfate. In some embodiments, the zinc source in (b) is diethylzinc.

In some embodiments, the indium salt in (b) is selected from the group consisting of indium bromide, indium chloride, indium fluoride, indium iodide, indium nitrate, indium perchlorate, indium hydroxide, indium acetate, and mixtures thereof. In some embodiments, the indium salt in (b) is selected from indium bromide, indium chloride, or indium acetate. In some embodiments, the indium salt in (b) is indium chloride. In some embodiments, the indium salt in (b) is indium acetate.

In some embodiments, the method of generating nanocrystal cores further includes:

(c) Contacting the reaction mixture in (b) with a zinc source and a selenium source.

In some embodiments, the zinc source in (c) is selected from diethyl zinc, dimethyl zinc, zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc carbonate , zinc cyanide, zinc nitrate, zinc oxide, zinc peroxide, zinc perchlorate and zinc sulfate. In some embodiments, the zinc source in (c) is diethylzinc.

In some embodiments, the selenium source in (c) is selected from trioctylphosphine selenide, tris(n-butyl)phosphine selenide, tris(sec-butyl)phosphine selenide, tris(tert-butyl)phosphine selenide Phosphine, trimethylphosphine selenide, triphenylphosphine selenide, diphenylphosphine selenide, phenylphosphine selenide, cyclohexylphosphine selenide, octaselenol, dodeceselenol, selenol, elemental selenium, Hydrogen selenide, bis(trimethylsilyl)selenide and mixtures thereof. In some embodiments, the selenium source in (c) is trioctylphosphine selenide.

In some embodiments, mixing in (a) is performed at a temperature of 250°C to 350°C. In some embodiments, the mixing temperature in (a) is about 300°C.

In some embodiments, contacting in (b) is performed at a temperature of 250°C to 350°C. In some embodiments, contacting in (b) is performed at a temperature of about 300°C.

In some embodiments, the contact in (b) further comprises at least one ligand.

In some embodiments, the contacting in (c) is at a temperature between 250°C and 350°C. In some embodiments, the contacting in (c) is at a temperature of about 300°C.

In some embodiments, the contact in (c) further comprises at least one ligand. In some embodiments, at least one ligand is trioctylphosphine or diphenylphosphine.

In some embodiments, the selenium source in (a) is trioctylphosphine selenide, the zinc source in (b) is diethylzinc, and the indium salt in (b) is indium chloride.

In some embodiments, the selenium source in (a) and (c) is trioctylphosphine selenide, the zinc source in (b) and (c) is diethylzinc, and the indium salt in (b) is Indium chloride.

The present disclosure relates to a method of producing a nanostructure comprising a core and at least one shell, the method comprising:

(d) mixing nanocrystals prepared by the methods described herein with a solution containing a zinc source and a sulfur source; and

(e) optionally repeat (d);

to produce a nanostructure comprising a core and at least one shell.

In some embodiments, the mixing temperature in (d) is from 20°C to 310°C. In some embodiments, mixing in (d) is performed at a temperature of 20°C to 100°C.

In some embodiments, the zinc source of (d) is selected from the group consisting of diethyl zinc, dimethyl zinc, zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc carbonate, Zinc cyanide, zinc nitrate, zinc oleate, zinc oxide, zinc peroxide, zinc perchlorate, zinc sulfate, zinc caproate, zinc octoate, zinc laurate, zinc myristate, zinc palmitate, zinc stearate , zinc dithiocarbamate, zinc oleate, zinc caproate, zinc octoate, zinc laurate, zinc myristate, zinc palmitate, zinc stearate, zinc dithiocarbamate or mixtures thereof.

In some embodiments, the sulfur source of (d) is selected from the group consisting of elemental sulfur, octyl mercaptan, dodecyl mercaptan, octadecanethiol, tributylphosphine sulfide, cyclohexyl isothiocyanate, alpha- Toluene mercaptan, ethylene trithiocarbonate, allyl mercaptan, bis(trimethylsilyl) sulfide, trioctylphosphine sulfide and mixtures thereof.

The present disclosure relates to a method of producing a nanostructure comprising a core, a buffer layer and at least one shell, the method comprising:

(d) mixing nanocrystals prepared by the methods described herein with a solution containing a zinc source and a selenium source;

(e) optionally repeat (d);

(f) mixing the reaction mixture of (e) with a solution containing a zinc source and a sulfur source; and

(g) optionally repeat (f);

To produce a nanostructure comprising a core, a buffer layer and at least one shell.

In some embodiments, mixing in (d) is performed at a temperature of 20°C to 310°C. In some embodiments, mixing in (d) is performed at a temperature of 20°C to 100°C.

In some embodiments, the zinc source of (d) is selected from the group consisting of diethyl zinc, dimethyl zinc, zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc carbonate, Zinc cyanide, zinc nitrate, zinc oleate, zinc oxide, zinc peroxide, zinc perchlorate, zinc sulfate, zinc caproate, zinc octoate, zinc laurate, zinc myristate, zinc palmitate, zinc stearate , zinc dithiocarbamate, zinc oleate, zinc caproate, zinc octoate, zinc laurate, zinc myristate, zinc palmitate, zinc stearate, zinc dithiocarbamate or mixtures thereof.

In some embodiments, the selenium source of (d) is selected from trioctylphosphine selenide, tris(n-butyl)phosphine selenide, tris(sec-butyl)phosphine selenide, tris(tert-butyl)phosphine selenide , trimethylphosphine selenide, triphenylphosphine selenide, diphenylphosphine selenide, phenylphosphine selenide, cyclohexylphosphine selenide, octaselenol, dodeceselenol, selenol, elemental selenium, selenium Hydrogen, bis(trimethylsilyl)selenide and mixtures thereof.

In some embodiments, the zinc source of (f) is selected from the group consisting of diethyl zinc, dimethyl zinc, zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc carbonate, Zinc cyanide, zinc nitrate, zinc oleate, zinc oxide, zinc peroxide, zinc perchlorate, zinc sulfate, zinc caproate, zinc octoate, zinc laurate, zinc myristate, zinc palmitate, zinc stearate , zinc dithiocarbamate, zinc oleate, zinc caproate, zinc octoate, zinc laurate, zinc myristate, zinc palmitate, zinc stearate, zinc dithiocarbamate or mixtures thereof.

In some embodiments, the sulfur source of (f) is selected from the group consisting of elemental sulfur, octyl mercaptan, dodecyl mercaptan, octadecanethiol, tributylphosphine sulfide, cyclohexyl isothiocyanate, alpha- Toluene mercaptan, ethylene trithiocarbonate, allyl mercaptan, bis(trimethylsilyl) sulfide, trioctylphosphine sulfide and mixtures thereof.

In some embodiments, contacting in (e) is performed at a temperature of 200°C to 350°C.

In some embodiments, contacting in (f) is performed at a temperature of 200°C to 350°C. In some embodiments, the contact temperature in (f) is about 310°C.

In some embodiments, the mixture in (d) further includes at least one ligand. In some embodiments, the at least one ligand is selected from trioctylphosphine oxide, trioctylphosphine, diphenylphosphine, triphenylphosphine oxide, and tributylphosphine oxide. In some embodiments, at least one ligand is trioctylphosphine or trioctylphosphine oxide.

In some embodiments, the mixture in (f) further includes at least one ligand.

In some embodiments, the at least one ligand is selected from trioctylphosphine oxide, trioctylphosphine, diphenylphosphine, triphenylphosphine oxide, and tributylphosphine oxide. In some embodiments, at least one ligand is trioctylphosphine or trioctylphosphine oxide.

The present disclosure relates to a light emitting diode, including:

(a) Anode;

(b) cathode; and

(c) Light-emitting layer containing nanostructures.

In some embodiments, the light emitting diode further includes a hole transport layer. In some embodiments, the hole transport layer includes a material selected from the group consisting of amines, triarylamines, thiophenes, carbazoles, phthalocyanines, porphyrins, and combinations thereof. In some embodiments, the hole transport layer includes N,N'-bis(naphth-1-yl)-N,N'-bis(4-vinylphenyl)-4,4'-diamine.

In some embodiments, the light emitting diode further includes an electron transport layer. In some embodiments, the electron transport layer comprises imidazole, pyridine, pyrimidine, pyridazine, pyrazine, oxadiazole, quinoline, quinoxaline, anthracene, benzanthracene, pyrene, perylene, benzo Materials of imidazoles, triazines, ketones, phosphine oxides, phenazines, phenanthrolines, triarylboranes, metal oxides and combinations thereof. In some embodiments, the electron transport layer includes 1,3-bis(3,5-dipyridin-3-ylphenyl)benzene (B3PyPB), bathocuproine, bathophenanthroline, 3-(dipyridin-3-ylphenyl)benzene (B3PyPB), Phenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole, 2-(4-biphenyl)-5-phenyl- 1,3,4-oxadiazole, 3,5-bis(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole, bis(8-hydroxy-2-methyl Quinoline)-(4-phenylphenoxy)aluminum, 2,5-bis(1-naphthyl)-1,3,4-oxadiazole, 3,5-diphenyl-4-(1 -naphthyl)-1H-1,2,4-triazole, 1,3,5-tris(m-pyridin-3-ylphenyl)benzene (TmPyPB), 2,2',2″-(1, 3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi), tris-(8-hydroxyquinoline)aluminum, TiO ₂ , ZnO, SnO ₂ , _SiO2 , _ZrO2 , or ZnMgO. In some embodiments, the electron transport layer includes ZnMgO.

Description of drawings

Figure 1 is a line graph showing the emission wavelength of a nanocrystal core containing (1) pure ZnSe; (2) ZnSe doped with 1.69% In using InCl as the In precursor; ( ₃ ) doped ZnSe with 0.597% In, using In(OC(=O) _CH3 ) ₃ as the In precursor; and (4) ZnSe doped with 0.270% In, using _InCl3 as the In precursor.

Figure 2 is the photoluminescence spectrum of ZnSe/ZnS quantum dots containing nanocrystalline cores prepared using undoped ZnSe.

Figure 3 is _{the photoluminescence spectrum of indium-doped ZnSe/ZnS quantum dots containing nanocrystalline cores with 0.112% In prepared using In(OC(=O)CH3)3 as} In precursor.

Figure 4 is (1) a ZnSe/ZnS quantum dot containing a nanocrystalline core prepared using undoped ZnSe; and (2) a ZnSe/ZnS quantum dot containing a nanocrystalline core prepared using _InCl as the In precursor with 0.597% In. Electroluminescence spectrum of indium-doped ZnSe/ZnS quantum dots.

Figure 5 is a graph showing the use of (1) ZnSe/ZnS quantum dots containing nanocrystalline cores prepared using undoped ZnSe; and (2) nanocrystalline cores containing 0.597% In prepared using _InCl3 as the In precursor. Line graph of the lifetime of devices prepared by indium-doped ZnSe/ZnS quantum dots.

Figure 6 is _{the electroluminescence spectrum of indium-doped ZnSe/ZnS quantum dots containing nanocrystalline cores with 0.112% In prepared using In(OC(=O)CH3)3 as} In precursor.

Detailed ways

definition

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The following definitions are supplementary to those in the art and specific to this application, and should not be transferred to any related or unrelated context, e.g., any commonly owned patents or applications. Although any methods and materials similar or equivalent to those described herein can be used in the practice of testing of the present invention, the preferred materials and methods are described herein. Accordingly, the terminology used herein is for the purpose of describing particular embodiments only and is not limiting.

As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a "nanostructure" includes a plurality of such nanostructures, and so on.

The term "about" as used herein means that the value of a given quantity varies by +/-10% of the value so described, or +/-5% of the value, or +/1% of the value. For example, "about 100 nm" encompasses a range of sizes from 90 nm to 110 nm (inclusive).

A "nanostructure" is a structure that has at least one dimensional region or characteristic dimension less than about 500 nm in size. In some embodiments, the nanostructures have dimensions of less than about 200 nm, less than about 100 nm, less than about 50 nm, less than about 20 nm, or less than about 10 nm. Typically, the area or feature dimension will be along the smallest axis of the structure. Examples of such structures include nanowires, nanorods, nanotubes, branched nanostructures, nanotetrapods, tripods, bipods, nanocrystals/nanodots, quantum dots, nanoparticles wait. Nanostructures may be, for example, substantially crystalline, substantially monocrystalline, polycrystalline, amorphous, or combinations thereof. In some embodiments, each of the three dimensions of the nanostructure has a size of less than about 500 nm, less than about 200 nm, less than about 100 nm, less than about 50 nm, less than about 20 nm, or less than about 10 nm.

When used in reference to nanostructures, the term "heterostructure" refers to nanostructures characterized by at least two different and/or distinguishable material types. Typically, one region of the nanostructure contains a first material type and a second region of the nanostructure contains a second material type. In certain embodiments, a nanostructure includes a core of a first material and at least one shell of a second (or third, etc.) material, where different material types, e.g., about the long axis of the nanowire, branching the arms of the nanowire The long axis or center radial distribution of the nanocrystal. A shell may, but need not, completely cover adjacent material to be considered a shell, or for a nanostructure to be considered a heterostructure; for example, a nanocrystal characterized by a core of one material covered with islands of a second material is heterogeneous structure. In other embodiments, different material types are distributed at different locations within the nanostructure; for example, along the main (long) axis of the nanowire or along the long axis of the arms of a branched nanowire. Different regions within the heterostructure may contain completely different materials, or different regions may contain a matrix material (eg, silicon) with different dopants or different concentrations of the same dopant.

As used herein, the "diameter" of a nanostructure refers to the diameter of a cross-section perpendicular to a first axis of the nanostructure, where the first axis has the greatest difference in length relative to the second and third axes (the second and third axes). axes are the two axes whose lengths are closest to being equal to each other). The first axis is not necessarily the longest axis of the nanostructure; for example, for a disk-shaped nanostructure, the cross-section is a substantially circular cross-section perpendicular to the short longitudinal axis of the disk. Where the cross-section is not circular, the diameter is the average of the major and minor axes of the cross-section. For elongated or high aspect ratio nanostructures, such as nanowires, the diameter is measured across a cross-section perpendicular to the longest axis of the nanowire. For spherical nanostructures, the diameter is measured from side to side through the center of the sphere.

When used with respect to nanostructures, the term "crystalline" or "elementary crystalline" refers to the fact that nanostructures typically exhibit long-range order in one or more dimensions of the structure. Those skilled in the art will understand that the term "long-range order" will depend on the absolute size of the particular nanostructure, since the ordering of a single crystal cannot extend beyond the boundaries of the crystal. In this context, "long-range order" means essentially ordered over at least a large portion of the nanostructure scale. In some cases, the nanostructure may have an oxide or other coating, or may include a core and at least one shell. In this case, it will be understood that the oxide, shell, or other coating may, but need not, exhibit such ordering (eg, it may be amorphous, polycrystalline, or otherwise). In this context, the phrase "crystalline", "substantially crystalline", "substantially single crystalline" or "single crystal" refers to the central core of the nanostructure (excluding coatings or shells). The term "crystalline" or "substantially crystalline" as used herein is also intended to include structures containing various defects, stacking faults, atomic substitutions, etc., so long as the structure exhibits substantial long-range order (e.g., in nanostructures or at least 80% of the length of at least one axis of its core is ordered). Additionally, it should be understood that the interface between the core and the exterior of a nanostructure, or between the core and an adjacent shell, or between a shell and a second adjacent shell, may contain amorphous regions, and may even be amorphous. This does not prevent the nanostructure from being crystalline or substantially crystalline as defined herein.

When used in relation to a nanostructure, the term "single crystal" means that the nanostructure is essentially and consists essentially of a single crystal. "Single crystal" when used with respect to a nanostructured heterostructure comprising a core and one or more shells means that the core is substantially crystalline and contains substantially a single crystal.

"Nanocrystals" are nanostructures that are essentially single crystals. Thus, a nanocrystal has at least one domain or characteristic dimension that has a dimension less than about 500 nm. In some embodiments, the size of the nanocrystals is less than about 200 nm, less than about 100 nm, less than about 50 nm, less than about 20 nm, or less than about 10 nm. The term "nanocrystal" is intended to encompass substantially single-crystalline nanostructures that contain various defects, stacking faults, atomic substitutions, and the like, as well as substantially single-crystalline nanostructures that are free of such defects, errors, or substitutions. In the case of nanocrystal heterostructures that include a core and one or more shells, the core of the nanocrystal is typically substantially monocrystalline, but the shell need not be. In some embodiments, each of the three dimensions of the nanocrystal has a size of less than about 500 nm, less than about 200 nm, less than about 100 nm, less than about 50 nm, less than about 20 nm, or less than about 10 nm.

The term "quantum dot" (or "dot") refers to a nanocrystal exhibiting quantum confinement or exciton confinement. Quantum dots may be substantially homogeneous in material properties or, in certain embodiments, may be heterogeneous, such as including a core and at least one shell. The optical properties of quantum dots can be affected by their particle size, chemical composition, and/or surface composition, and can be determined by suitable optical tests available in the art. The ability to tune the size of nanocrystals, for example, in the range of about 1 nm and about 15 nm, enables light emission coverage across the spectrum, providing great versatility in color rendering.

A "ligand" is a molecule capable of interacting, whether weakly or strongly, with one or more faces of a nanostructure, such as through covalent, ionic, van der Waals or other molecular interactions with the surface of the nanostructure.

"Photoluminescence quantum yield" is, for example, the ratio of photons emitted to photons absorbed by a nanostructure or population of nanostructures. As is known in the art, quantum yield is typically determined by comparative methods using well-characterized standard samples with known quantum yield values.

"Peak emission wavelength" (PWL) is the wavelength at which the radiative emission spectrum of a light source reaches its maximum.

As used herein, the term "shell" refers to material deposited on a core or on a previously deposited shell of the same or different composition, and which results from the deposition of a single acting shell material. The exact shell thickness depends on the material as well as precursor input and transformation, and can be reported in nanometers or monolayers. As used herein, "target shell thickness" refers to the expected shell thickness used in calculating the required amount of precursor. As used herein, "actual shell thickness" refers to the amount of shell material actually deposited after synthesis, and can be measured by methods known in the art. For example, the actual shell thickness can be determined by comparing the particle size determined from transmission electron microscopy (TEM) images of the nanocrystals before and after shell synthesis.

As used herein, the term "monolayer" is a unit of measurement of shell thickness derived from the bulk crystal structure of the shell material as the closest distance between relevant lattice planes. For example, for cubic lattice structures, the thickness of a single layer is determined as the distance between adjacent lattice planes in the [111] direction. For example, a single layer of cubic ZnSe corresponds to a thickness of 0.328 nm, and a single layer of cubic ZnS corresponds to a thickness of 0.31 nm. The thickness of a single layer of alloy material can be determined from the alloy composition through Vegard's law.

As used herein, the term "full width at half maximum" (FWHM) is a measure of the size distribution of a quantum dot. The emission spectrum of quantum dots usually has the shape of a Gaussian curve. The width of the Gaussian curve is defined as FWHM and gives the concept of particle size distribution. Smaller FWHM corresponds to a narrower quantum dot nanocrystal size distribution. FWHM also depends on the emission wavelength maximum.

As used herein, the term "external quantum efficiency" (EQE) is the ratio of the number of photons emitted from a light-emitting diode (LED) to the number of electrons passing through the device. EQE measures how effectively an LED converts electrons into photons and allows them to escape. EQE can be measured using the following formula:

EQE=[Injection Efficiency]×[Solid State Quantum Yield]×[Extraction Efficiency]

in:

Injection efficiency = the proportion of electrons injected into the active region through the device;

Solid-state quantum yield = the proportion of all electron-hole recombination in the active region that is radiative and therefore produces photons; and

Extraction efficiency = the proportion of photons generated in the active region that escape from the device.

Unless otherwise expressly stated, the ranges set forth herein are inclusive.

Various additional terms are defined or otherwise characterized herein.

Generation of nanostructures

Methods for colloidal synthesis of various nanostructures are known in the art. Such methods include techniques for controlling the growth of nanostructures, for example, for controlling the size and/or shape distribution of the resulting nanostructures.

In typical colloidal synthesis, semiconductor nanostructures are prepared by rapidly injecting precursors that undergo pyrolysis into a hot solution (e.g., hot solvents and/or surfactants). Precursors can be injected simultaneously or sequentially. The precursors react rapidly to form nuclei. Nanostructure growth occurs by adding monomers to the core.

Surface interaction of surfactant molecules with nanostructures. At growth temperatures, surfactant molecules rapidly adsorb and desorb from the nanostructure surface, allowing the addition and/or removal of atoms in the nanostructure while inhibiting aggregation of the growing nanostructure. Typically, surfactants that coordinate weakly with the nanostructure surface allow rapid nanostructure growth, whereas surfactants that bind more strongly to the nanostructure surface result in slower nanostructure growth. Surfactants can also interact with the precursor (or precursors) to slow down the growth of nanostructures.

Nanostructure growth in the presence of a single surfactant usually results in spherical nanostructures. However, using a mixture of two or more surfactants allows for controlled growth such that non-spherical shapes can be produced if, for example, the two (or more) surfactants adsorb differentially to different crystalline phase faces of the growing nanostructure. Nano-structure.

Therefore, many parameters are known to influence nanostructure growth and can be manipulated independently or in combination to control the size and/or shape distribution of the resulting nanostructures. These include, for example, temperature (nucleation and/or growth), precursor composition, time-dependent precursor concentration, ratios of precursors to each other, surfactant composition, surfactant amounts and ratios of surfactants to each other and/or to Precursor ratio.

For example, in U.S. Patent Nos. 6,225,198, 6,322,901, 6,207,229, 6,607,829, 7,060,243, 7,374,824, 6,861,155, 7,125,605, 7,566,476, 8,158,193, and 8,101,234 and U.S. Patent Application Publication No. 2 Group II-VI nanoparticles are described in 011/0262752 and 2011/0263062 Synthesis of structures.

Although II-VI nanostructures such as CdSe/CdS/ZnS core/shell quantum dots can exhibit desirable luminescent properties, as mentioned above, issues such as the toxicity of cadmium limit the applications in which such nanostructures can be used. Less toxic alternatives with favorable luminescent properties are therefore highly desirable.

In some embodiments, the nanostructures are cadmium-free. As used herein, the term "cadmium-free" means that the nanostructure contains less than 100 ppm cadmium by weight. Restriction of Hazardous Substances (RoHS) compliance definition requires no more than 0.01% by weight (100ppm) cadmium in the original homogeneous precursor material. The cadmium content of the Cd-free nanostructures of the present invention is limited by the trace metal concentration in the precursor material. Trace metal (including cadmium) concentrations in Cd-free nanostructured precursor materials were measured by inductively coupled plasma mass spectrometry (ICP-MS) analysis and are at parts per billion (ppb) levels. In some embodiments, "cadmium-free" nanostructures contain less than about 50 ppm, less than about 20 ppm, less than about 10 ppm, or less than about 1 ppm cadmium.

Generation of Indium-Doped ZnSe Cores

The nanostructure consists of an indium-doped ZnSe core and a ZnS shell. In some embodiments, the nanostructures are indium-doped ZnSe/ZnS core/shell nanostructures. In some embodiments, the nanostructure is an indium-doped ZnSe/ZnSe/ZnS core/buffer/shell nanostructure.

As used herein, the term "nucleation period" refers to the formation of a core of indium-doped ZnSe nuclei. As used herein, the term "growth phase" refers to the growth process in which a layer of ZnS or ZnSe is applied to the core.

The diameter of the indium-doped ZnSe core can be controlled by varying the amount of precursor provided. The diameter of the indium-doped ZnSe core can be determined using techniques known to those skilled in the art. In some embodiments, the diameter of the indium-doped ZnSe core is determined using transmission electron microscopy (TEM).

In some embodiments, each indium-doped ZnSe core has a diameter from about 1.0 nm to about 7.0 nm, from about 1.0 nm to about 6.0 nm, from about 1.0 nm to about 5.0 nm, from about 1.0 nm to about 4.0 nm, from about 1.0nm-about 3.0nm, about 1.0nm-about 2.0nm, about 2.0nm-about 7.0nm, about 2.0nm-about 6.0nm, about 2.0nm-about 5.0nm, about 2.0nm-about 4.0nm, about 2.0nm - about 3.0nm, about 3.0nm - about 7.0nm, about 3.0nm - about 6.0nm, about 3.0nm - about 5.0nm, about 3.0nm - about 4.0nm, about 4.0nm - about 7.0nm, about 4.0nm - about 6.0nm, about 4.0nm to about 5.0nm, about 5.0nm to about 7.0nm, about 5.0nm to about 6.0nm, or about 6.0nm to about 7.0nm. In some embodiments, the indium-doped ZnSe core has a diameter of about 4.0 nm to about 5.0 nm.

In some embodiments, the invention provides a method of producing indium-doped ZnSe nanocrystals, comprising:

(a) mixing a source of selenium and at least one ligand to produce a reaction mixture; and

(b) contacting the reaction mixture obtained in (a) with a zinc source and an indium salt;

To provide indium-doped ZnSe nanocrystals.

In some embodiments, the method further includes:

(c) contacting the reaction mixture in (b) with a zinc source and a selenium source;

To provide indium-doped ZnSe nanocrystals.

In some embodiments, the selenium source is selected from trioctylphosphine selenide, tris(n-butyl)phosphine selenide, tris(sec-butyl)phosphine selenide, tris(tert-butyl)phosphine selenide, trimethyl Phosphine selenide, triphenylphosphine selenide, diphenylphosphine selenide, phenylphosphine selenide, cyclohexylphosphine selenide, octaselenol, dodeceselenol, selenol, elemental selenium, hydrogen selenide, bisselenide (Trimethylsilyl)selenide and mixtures thereof. In some embodiments, the selenium source is trioctylphosphine selenide (TOPSe).

In some embodiments, the zinc source is a dialkyl zinc compound. In some embodiments, the zinc source is diethyl zinc, dimethyl zinc, zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc carbonate, zinc cyanide, nitric acid Zinc, zinc oxide, zinc peroxide, zinc perchlorate or zinc sulfate. In some embodiments, the zinc source is diethyl zinc or dimethyl zinc. In some embodiments, the zinc source is diethylzinc.

In some embodiments, the indium salt is selected from the group consisting of indium bromide, indium chloride, indium fluoride, indium iodide, indium nitrate, indium perchlorate, indium hydroxide, indium acetate, and mixtures thereof. In some embodiments, the indium salt is indium chloride, indium bromide, or indium acetate. In some embodiments, the indium salt is indium chloride. In some embodiments, the indium salt is indium bromide. In some embodiments, the indium salt is indium acetate.

In some embodiments, the mole percentage of indium salt to zinc source is about 0.01% to about 2%, about 0.01% to about 1%, about 0.01% to about 0.5%, about 0.01% to about 0.1%, about 0.01% to about 0.05%, about 0.01% to about 0.03%, about 0.03% to about 2%, about 0.03% to about 1%, about 0.03% to about 0.5%, about 0.03% to about 0.1%, about 0.03% to about 0.05%, about 0.05% to about 2%, about 0.05% to about 1%, about 0.05% to about 0.5%, about 0.05% to about 0.1%, about 0.1% to about 2%, about 0.1% to about 1% , about 0.1% to about 0.5%, about 0.5% to about 2%, about 0.5% to about 1%, or about 1% to about 2%. In some embodiments, the mole percent of indium salt to zinc source is from about 0.1% to about 1%. In some embodiments, the mole percent of indium salt to zinc source is about 0.3%.

In some embodiments, the indium-doped ZnSe core is synthesized in the presence of at least one nanostructured ligand. Ligands can, for example, enhance the miscibility of the nanostructures in solvents or polymers (thus allowing the nanostructures to be distributed throughout the composition so that the nanostructures do not clump together), increase the quantum yield of the nanostructures and/or maintain nanostructures. Structural luminescence (for example, when nanostructures are incorporated into a matrix). In some embodiments, the ligands used for core synthesis and shell synthesis are the same. In some embodiments, the ligands used for core synthesis and shell synthesis are different. After synthesis, any ligands on the surface of the nanostructure can be exchanged with different ligands with other desired properties. Examples of ligands are disclosed in U.S. Patent Application Publication Nos. 2005/0205849, 2008/0105855, 2008/0118755, 2009/0065764, 2010/0140551, 2013/0345458, 2014/0151600, 2014/0264189, and 2014/00 01405 in.

In some embodiments, suitable ligands for the synthesis of nanostructured cores, including indium-doped ZnSe cores, are known to those skilled in the art. In some embodiments, the ligand is a fatty acid selected from the group consisting of lauric acid, caproic acid, myristic acid, palmitic acid, stearic acid, and oleic acid. In some embodiments, the ligand is an organophosphine or organophosphine oxide selected from trioctylphosphine oxide (TOPO), trioctylphosphine (TOP), diphenylphosphine (DPP), triphenylphosphine oxide and tributylphosphine oxide. In some embodiments, the ligand is an amine selected from the group consisting of dodecylamine, oleylamine, cetylamine, and octadecylamine. In some embodiments, the ligand is trioctylphosphine (TOP). In some embodiments, the ligand is oleylamine.

In some embodiments, indium-doped ZnSe cores are produced in the presence of a ligand mixture. In some embodiments, indium-doped ZnSe cores are produced in the presence of mixtures containing 2, 3, 4, 5, or 6 different ligands. In some embodiments, an indium-doped ZnSe core is produced in the presence of a mixture containing 3 different ligands. In some embodiments, the ligand mixture includes oleylamine, diphenylphosphine, and trioctylphosphine.

In some embodiments, the selenium source and ligand are at 250°C to 350°C, 250°C to 320°C, 250°C to 300°C, 250°C to 290°C, 250°C to 280°C, 250°C to 270°C, 270°C to 350℃, 270℃ to 320℃, 270℃ to 300℃, 270℃ to 290℃, 270℃ to 280℃, 280℃ to 350℃, 280℃ to 320℃, 280℃ to 300℃, 280℃ to 290℃ ℃, 290 ℃ to 350 ℃, 290 ℃ to 320 ℃, 290 ℃ to 300 ℃, 300 ℃ to 350 ℃, 300 ℃ to 320 ℃ or 320 ℃ to 350 ℃ reaction temperature. In some embodiments, the selenium source and ligand are mixed at a reaction temperature of about 300°C.

In some embodiments, the reaction mixture after mixing the selenium source and the ligand is maintained at the reaction temperature for 2 to 20 minutes, 2 to 15 minutes, 2 to 10 minutes, 2 to 8 minutes, 2 to 5 minutes, 5 to 20 minutes , 5 to 15 minutes, 5 to 10 minutes, 5 to 8 minutes, 8 to 20 minutes, 8 to 15 minutes, 8 to 10 minutes, 10 to 20 minutes, 10 to 15 minutes or 15 to 20 minutes.

In some embodiments, at 250°C to 350°C, 250°C to 320°C, 250°C to 300°C, 250°C to 290°C, 250°C to 280°C, 250°C to 270°C, 270°C to 350°C, 270 ℃ to 320℃, 270℃ to 300℃, 270℃ to 290℃, 270℃ to 280℃, 280℃ to 350℃, 280℃ to 320℃, 280℃ to 300℃, 280℃ to 290℃, 290℃ to Adding the indium salt and the zinc source to the ligand source and the selenium source at a reaction temperature of 350°C, 290°C to 320°C, 290°C to 300°C, 300°C to 350°C, 300°C to 320°C, or 320°C to 350°C in the mixture. In some embodiments, the indium salt and zinc source are added to the mixture of ligand source and selenium source at a reaction temperature of about 300°C.

In some embodiments, the reaction mixture - after adding the indium salt and zinc source - is maintained at the reaction temperature for 2 to 20 minutes, 2 to 15 minutes, 2 to 10 minutes, 2 to 8 minutes, 2 minutes to 5 minutes, 5 minutes to 20 minutes, 5 minutes to 15 minutes, 5 minutes to 10 minutes, 5 minutes to 8 minutes, 8 minutes to 20 minutes, 8 minutes to 15 minutes, 8 minutes to 10 minutes, 10 minutes to 20 minutes, 10 minutes to 15 minutes or 15 to 20 minutes.

In some embodiments, after adding the indium salt and the zinc source, the reaction mixture is contacted with the zinc source and the selenium source. In some embodiments, the zinc source and the selenium source are at 250°C to 350°C, 250°C to 320°C, 250°C to 300°C, 250°C to 290°C, 250°C to 280°C, 250°C to 270°C, 270°C to 350℃, 270℃ to 320℃, 270℃ to 300℃, 270℃ to 290℃, 270℃ to 280℃, 280℃ to 350℃, 280℃ to 320℃, 280℃ to 300℃, 280℃ to 290℃ ℃, 290°C to 350°C, 290°C to 320°C, 290°C to 300°C, 300°C to 350°C, 300°C to 320°C, or 320°C and 350°C. In some embodiments, the zinc source and selenium source are added to the reaction mixture at a reaction temperature of about 280°C.

In some embodiments, the zinc source and the selenium source are present at 2 to 60 minutes, 2 to 30 minutes, 2 to 20 minutes, 2 to 15 minutes, 2 to 10 minutes, 2 to 8 minutes, 2 to 5 minutes, 5 to 60 minutes minutes, 5 to 30 minutes, 5 to 20 minutes, 5 to 15 minutes, 5 to 10 minutes, 5 to 8 minutes, 8 to 60 minutes, 8 to 30 minutes, 8 to 20 minutes, 8 to 15 minutes, 8 to 10 minutes, 10 to 60 minutes, 10 to 30 minutes, 10 to 20 minutes, 10 to 15 minutes, 15 to 60 minutes, 15 to 30 minutes, 15 to 20 minutes, 20 to 60 minutes, 20 minutes to 30 minutes, or 30 to Added within a 60 minute period. In some embodiments, the zinc source and selenium source are added over a period of 20 to 60 minutes.

In some embodiments, after adding the zinc source and selenium source, the reaction mixture is maintained at the reaction temperature for 2 to 20 minutes, 2 to 15 minutes, 2 to 10 minutes, 2 to 8 minutes, 2 to 5 minutes, 5 to 20 minutes minutes, 5 to 15 minutes, 5 to 10 minutes, 5 to 8 minutes, 8 to 20 minutes, 8 to 15 minutes, 8 to 10 minutes, 10 to 20 minutes, 10 to 15 minutes or 15 to 20 minutes. In some embodiments, after adding the zinc source and selenium source, the reaction mixture is maintained at the reaction temperature for 2 to 10 minutes.

To prevent precipitation of the indium-doped ZnSe core with the addition of additional precursors, additional ligands can be added during the growth phase. If too many ligands are added during the initial nucleation period, the concentrations of zinc source, selenium source, and indium salt will be too low and prevent efficient nucleation. Therefore, ligands are added slowly throughout the growth phase. In some embodiments, the additional ligand is oleylamine.

After the indium-doped ZnSe cores reach the desired thickness and diameter, they can be cooled. In some embodiments, the indium-doped ZnSe core is cooled to room temperature. In some embodiments, an organic solvent is added to dilute the reaction mixture containing the indium-doped ZnSe core.

In some embodiments, the organic solvent is hexane, pentane, toluene, benzene, diethyl ether, acetone, ethyl acetate, dichloromethane (methylene chloride), chloroform, dimethylformamide, or N-methyl Pyrrolidone. In some embodiments, the organic solvent is toluene.

In some embodiments, an indium-doped ZnSe core is isolated. In some embodiments, the indium-doped ZnSe core is isolated by precipitating the indium-doped ZnSe core from the solvent. In some embodiments, the indium-doped ZnSe core is isolated by precipitation with ethanol.

In some embodiments, the nanostructured indium-doped ZnSe core of the present invention has an indium-doped ZnSe core with a thickness of between 40% to 90%, 40% to 80%, 40% to 70%, 40% to 60%, 40% to 50%, 50% to 90%, 50% to 80%, 50% to 70%, 50% to 60%, 60% to 90%, 60% to 80%, 60% to 70%, 70% to 90%, 70% to 80% or 80% to 90% indium doped ZnSe content by weight.

In some embodiments, the molar ratio of zinc to selenium of the nanostructured indium-doped ZnSe core of the present invention is about 1:1 to about 1:0.8, about 1:1 to about 1:0.9, about 1:1 and about 1:0.92 or about 1:1 and about 1:0.94.

Generation of ZnSe buffer layer

In some embodiments, the nanostructure includes a buffer layer between the core and the shell. In some embodiments, the buffer layer is a ZnSe buffer layer.

In some embodiments, the ZnSe buffer layer facilitates lattice straining between the In-doped ZnSe core and ZnS shell.

In some embodiments, a single ZnSe monolayer has a thickness of approximately 0.328 nm.

In some embodiments, the number of monolayers in the ZnSe buffer layer is 0.25 to 10, 0.25 to 8, 0.25 to 7, 0.25 to 6, 0.25 to 5, 0.25 to 4, 0.25 to 3, 0.25 to 2, 2 to 10 , 2 to 8, 2 to 7, 2 to 6, 2 to 5, 2 to 4, 2 to 3, 3 to 10, 3 to 8, 3 to 7, 3 to 6, 3 to 5, 3 to 4, 4 to 10, 4 to 8, 4 to 7, 4 to 6, 4 to 5, 5 to 10, 5 to 8, 5 to 7, 5 to 6, 6 to 10, 6 to 8, 6 to 7, 7 to 10 , 7 to 8 or 8 to 10. In some embodiments, the ZnSe buffer layer contains 2 to 6 monolayers. In some embodiments, the ZnSe buffer layer contains 3 to 5 monolayers.

The thickness of the ZnSe buffer layer can be controlled by varying the amount of precursor provided. For a given layer, at least one precursor is optionally provided in an amount such that when the growth reaction is substantially complete, the layer has a predetermined thickness. If more than one different precursor is provided, the amount of each precursor may be so limited, or one precursor may be provided in a limited amount and the other precursors in excess.

The thickness of each ZnSe layer of the ZnSe buffer layer can be determined using techniques known to those skilled in the art. The thickness of each layer was determined by comparing the diameter of the indium-doped ZnSe/ZnSe core/buffer layer before and after adding each layer. In some embodiments, the diameter of the indium-doped ZnSe/ZnSe core/buffer layer is determined by transmission electron microscopy before and after the addition of each layer.

In some embodiments, the ZnSe buffer layer has a thickness of 0.08nm to 3.5nm, 0.08nm to 2nm, 0.08nm to 0.9nm, 0.08nm to 0.7nm, 0.08nm to 0.5nm, 0.08nm to 0.2nm, 0.2nm to 3.5nm, 0.2nm to 2nm, 0.2nm to 0.9nm, 0.2nm to 0.7nm, 0.2nm to 0.5nm, 0.5nm to 3.5nm, 0.5nm to 2nm, 0.5nm to 0.9nm, 0.5nm to 0.7nm, 0.7 nm to 3.5nm, 0.7nm to 2nm, 0.7nm to 0.9nm, 0.9nm to 3.5nm, 0.9nm to 2nm or 2nm to 3.5nm. In some embodiments, the ZnSe buffer layer has a thickness of about 2 nm to about 3 nm.

In some embodiments, the invention provides a method of preparing nanostructures, comprising:

(a) mixing a source of selenium and at least one ligand to produce a reaction mixture; and

(b) contacting the reaction mixture obtained in (a) with a zinc source and an indium salt;

(c) contacting the reaction mixture in (b) with a zinc source and a selenium source to provide an indium-doped ZnSe core;

(d) contacting the indium-doped ZnSe core of (c) with a solution containing a zinc source and a selenium source; and (e) repeating (d) to provide an indium-doped ZnSe/ZnSe core/buffer nanostructure.

The thickness of the ZnSe buffer layer can be conveniently controlled by controlling the amount of precursor provided. For a given layer, at least one precursor is optionally provided in an amount such that when the growth reaction is substantially complete, the layer has a predetermined thickness. If more than one different precursor is provided, the amount of each precursor may be so limited, or one precursor may be provided in a limited amount and the other precursors in excess. Appropriate amounts of precursor can be easily calculated for various resulting shell thicknesses. For example, the indium-doped ZnSe/ZnSe core/buffer layer can be dispersed in solution after its synthesis and purification, and its concentration can be calculated by UV/Vis spectroscopy, for example using Beer-Lambert's law. The extinction coefficient can be obtained from bulk indium-doped ZnSe and bulk ZnSe. The size of the indium-doped ZnSe/ZnSe core/buffer layer can be determined, for example, by the exciton peaks of UV/Vis absorption spectra and physical modeling based on quantum confinement. Knowing the particle size, molar amount, and desired thickness of the shell-forming material, the amount of precursor can be calculated using bulk crystal parameters (ie, the thickness of a layer of shell-forming material).

In some embodiments, the buffer layer precursor in contact with the indium-doped ZnSe core includes a zinc source and a selenium source.

In some embodiments, the zinc source is a dialkyl zinc compound. In some embodiments, the zinc source is zinc carboxylate. In some embodiments, the zinc source is diethyl zinc, dimethyl zinc, zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc carbonate, zinc cyanide, nitric acid Zinc, zinc oleate, zinc oxide, zinc peroxide, zinc perchlorate, zinc sulfate, zinc caproate, zinc octoate, zinc laurate, zinc myristate, zinc palmitate, zinc stearate, dithioamino acid zinc formate or their mixtures. In some embodiments, the zinc source is zinc oleate, zinc caproate, zinc octoate, zinc laurate, zinc myristate, zinc palmitate, zinc stearate, zinc dithiocarbamate, or mixtures thereof. In some embodiments, the zinc source is zinc oleate.

In some embodiments, the selenium source is an alkyl-substituted selenourea. In some embodiments, the selenium source is phosphine selenide. In some embodiments, the selenium source is selected from trioctylphosphine selenide, tris(n-butyl)phosphine selenide, tris(sec-butyl)phosphine selenide, tris(tert-butyl)phosphine selenide, trimethyl Phosphine selenide, triphenylphosphine selenide, diphenylphosphine selenide, phenylphosphine selenide, tricyclohexylphosphine selenide, cyclohexylphosphine selenide, 1-octaneselenol, 1-dodecyl Selenol, selenol, elemental selenium, hydrogen selenide, bis(trimethylsilyl)selenide, selenourea and mixtures thereof. In some embodiments, the selenium source is tris(n-butyl)phosphine selenide, tris(sec-butyl)phosphine selenide, or tris(tert-butyl)phosphine selenide. In some embodiments, the selenium source is trioctylphosphine selenide.

In some embodiments, the ZnSe buffer layer is synthesized in the presence of at least one nanostructured ligand. Ligands can, for example, enhance the miscibility of the nanostructures in solvents or polymers (thus allowing the nanostructures to be distributed throughout the composition so that the nanostructures do not clump together), increase the quantum yield of the nanostructures and/or maintain nanostructures. Structured luminescence (e.g. when incorporating nanostructures into a matrix). In some embodiments, the ligands used for nucleosynthesis and buffer layer synthesis are the same. In some embodiments, the ligands used for nucleosynthesis and buffer layer synthesis are different. After synthesis, any ligands on the surface of the nanostructure can be exchanged with different ligands with other desired properties.

In some embodiments, suitable ligands for the synthesis of nanostructured buffer layers, including ZnSe buffer layers, are known to those skilled in the art. In some embodiments, the ligand is a fatty acid selected from the group consisting of lauric acid, caproic acid, myristic acid, palmitic acid, stearic acid, and oleic acid. In some embodiments, the ligand is an organophosphine or organophosphine oxide selected from trioctylphosphine oxide (TOPO), trioctylphosphine (TOP), diphenylphosphine (DPP), triphenylphosphine oxide, and triphenylphosphine oxide. Butylphosphine oxide. In some embodiments, the ligand is an amine selected from the group consisting of dodecylamine, oleylamine, cetylamine, and octadecylamine. In some embodiments, the ligand is trioctylphosphine (TOP). In some embodiments, the ligand is trioctylphosphine oxide.

In some embodiments, the ZnSe buffer layer is produced in the presence of a ligand mixture. In some embodiments, the ZnSe buffer layer is produced in the presence of a mixture containing 2, 3, 4, 5 or 6 different ligands. In some embodiments, the ZnSe buffer layer is produced in the presence of a mixture containing 2 different ligands. In some embodiments, the mixture of ligands includes trioctylphosphine and trioctylphosphine oxide. Examples of ligands are disclosed in U.S. Patent Application Publication Nos. 2005/0205849, 2008/0105855, 2008/0118755, 2009/0065764, 2010/0140551, 2013/0345458, 2014/0151600, 2014/0264189, and 2014/00 01405 in.

In some embodiments, in the buffer layer phase, the indium-doped ZnSe core, zinc source, and selenium source are at 250°C to 350°C, 250°C to 320°C, 250°C to 300°C, 250°C to 290°C, 250 ℃ to 280℃, 250℃ to 270℃, 270℃ to 350℃, 270℃ to 320℃, 270℃ to 300℃, 270℃ to 290℃, 270℃ to 280℃, 280℃ to 350℃, 280℃ to 320℃, 280℃ to 300℃, 280℃ to 290℃, 290℃ to 350℃, 290℃ to 320℃, 290℃ to 300℃, 300℃ to 350℃, 300℃ to 320℃ or 320℃ to 350℃ combination at the reaction temperature. In some embodiments, the indium-doped ZnSe core, zinc source, and selenium source are combined at a reaction temperature of about 300°C.

In some embodiments, the reaction mixture - after combining the indium-doped ZnSe core, zinc source and selenium source - is maintained at the reaction temperature for 2 to 20 minutes, 2 to 15 minutes, 2 to 10 minutes, 2 to 8 minutes , 2 to 5 minutes, 5 to 20 minutes, 5 to 15 minutes, 5 to 10 minutes, 5 to 8 minutes, 8 to 20 minutes, 8 to 15 minutes, 8 to 10 minutes, 10 to 20 minutes, 10 to 15 minutes Or 15 and 20 minutes.

In some embodiments, further additional precursors are added to the reaction mixture. Typically, additional precursors are provided after the reaction of the previous layer is substantially complete (eg, when at least one previous precursor is depleted or removed from the reaction or when no additional growth is detected). In some additives, an additional precursor added is a source of selenium. Further precursor additions create additional layers.

After the indium-doped ZnSe/ZnSe core/buffer nanostructures reach the desired thickness and diameter, they can be cooled. In some embodiments, the indium-doped ZnSe/ZnSe core/buffer nanostructure is cooled to room temperature. In some embodiments, an organic solvent is added to dilute the reaction mixture comprising the indium-doped ZnSe/ZnSe core/buffer nanostructures.

In some embodiments, the organic solvent is hexane, pentane, toluene, benzene, diethyl ether, acetone, ethyl acetate, dichloromethane (methylene chloride), chloroform, dimethylformamide, methanol, ethanol, or N-methylpyrrolidone. In some embodiments, the organic solvent is toluene.

In some embodiments, an indium-doped ZnSe/ZnSe core/buffer nanostructure is isolated. In some embodiments, the indium-doped ZnSe/ZnSe core/buffer nanostructure is isolated by precipitating the indium-doped ZnSe/ZnSe core/buffer nanostructure using an organic solvent. In some embodiments, the indium-doped ZnSe/ZnSe core/buffer nanostructures are isolated by precipitation with ethanol.

The number of layers determines the size of the indium-doped ZnSe/ZnSe core/buffer nanostructure. The dimensions of the indium-doped ZnSe/ZnSe core/buffer nanostructures can be determined using techniques known to those skilled in the art. In some embodiments, transmission electron microscopy is used to determine the dimensions of the indium-doped ZnSe/ZnSe core/buffer nanostructures. In some embodiments, the indium-doped ZnSe/ZnSe core/buffer layer nanostructures have an average diameter of 1 nm to 15 nm, 1 nm to 10 nm, 1 nm to 9 nm, 1 nm to 8 nm, 1 nm to 7 nm, 1 nm to 6 nm, 1 nm to 5 nm , 5nm to 15nm, 5nm to 10nm, 5nm to 9nm, 5nm to 8nm, 5nm to 7nm, 5nm to 6nm, 6nm to 15nm, 6nm to 10nm, 6nm to 9nm, 6nm to 8nm, 6nm to 7nm, 7nm to 15nm, 7nm to 10nm, 7nm to 9nm, 7nm 8nm, 8nm to 15nm, 8nm to 10nm, about 8nm to 9nm, 9nm to 15nm, 9nm to 10nm or 10nm to 15nm. In some embodiments, the indium-doped ZnSe/ZnSe core/buffer nanostructures have an average diameter of about 7 nm.

In some embodiments, quantum confinement is used to determine the diameter of the indium-doped ZnSe/ZnSe core/buffer nanostructure.

production of shell

In some embodiments, the nanostructures of the present invention include a core and at least one shell. In some embodiments, the nanostructures of the present invention include a core and at least two shells. In some embodiments, the nanostructures of the present invention include a core, a buffer layer, and at least one shell. In some embodiments, the nanostructures of the present invention include a core, a buffer layer, and at least two shells. Shells can, for example, increase the quantum yield and/or stability of the nanostructure. In some embodiments, the core and shell comprise different materials. In some embodiments, the nanostructures comprise shells of different shell materials.

In some embodiments, a shell comprising a mixture of Group II and Group VI elements is deposited on a core, core/buffer, core/shell or core/buffer/shell structure. In some embodiments, the deposited shell is a mixture of at least two of a zinc source, a selenium source, a sulfur source, a tellurium source, and a cadmium source. In some embodiments, the deposited shell is a mixture of two of a zinc source, a selenium source, a sulfur source, a tellurium source, and a cadmium source. In some embodiments, the deposited shell is a mixture of three of a zinc source, a selenium source, a sulfur source, a tellurium source, and a cadmium source. In some embodiments, the shell includes zinc and sulfur; zinc and selenium; zinc, sulfur and selenium; zinc and tellurium; zinc, tellurium and sulfur; zinc, tellurium and selenium; zinc, cadmium and sulfur; zinc, cadmium and selenium; Cadmium and sulfur; cadmium and selenium; cadmium, selenium and sulfur; cadmium, zinc and sulfur; cadmium, zinc and selenium; or cadmium, zinc, sulfur and selenium.

In some embodiments, the shell contains more than one single layer of shell material. The number of monolayers is the average of all nanostructures; therefore, the number of monolayers in a shell can be a fraction. In some embodiments, the number of monolayers in the shell is 0.25 to 10, 0.25 to 8, 0.25 to 7, 0.25 to 6, 0.25 to 5, 0.25 to 4, 0.25 to 3, 0.25 to 2, 2 to 10, 2 to 8, 2 to 7, 2 to 6, 2 to 5, 2 to 4, 2 to 3, 3 to 10, 3 to 8, 3 to 7, 3 to 6, 3 to 5, 3 to 4, 4 to 10 , 4 to 8, 4 to 7, 4 to 6, 4 to 5, 5 to 10, 5 to 8, 5 to 7, 5 to 6, 6 to 10, 6 to 8, 6 to 7, 7 to 10, 7 Or 8 to 10. In some embodiments, the shell contains 3 to 5 monolayers.

The thickness of the shell can be controlled by varying the amount of precursor provided. For a given shell thickness, at least one precursor is optionally provided in an amount such that when the growth reaction is substantially complete, a shell of a predetermined thickness is obtained. If more than one different precursor is provided, the amount of each precursor may be limited, or one precursor may be provided in a limited amount and the other precursors may be provided in excess.

The thickness of each shell can be determined using techniques known to those skilled in the art. In some embodiments, the thickness of each shell is determined by comparing the average diameter of the nanostructures before and after addition of each shell. In some embodiments, the average diameter of the nanostructures before and after addition of each shell is determined by TEM. In some embodiments, the thickness of each shell is 0.05nm to 3.5nm, 0.05nm to 2nm, 0.05nm to 0.9nm, 0.05nm to 0.7nm, 0.05nm to 0.5nm, 0.05nm to 0.3nm, 0.05nm to 0.1nm, 0.1nm to 3.5nm, 0.1nm to 2nm, 0.1nm to 0.9nm, 0.1nm to 0.7nm, 0.1nm to 0.5nm, 0.1nm to 0.3nm, 0.3nm to 3.5nm, 0.3nm to 2nm, 0.3 nm to 0.9nm, 0.3nm to 0.7nm, 0.3nm to 0.5nm, 0.5nm to 3.5nm, 0.5nm to 2nm, 0.5nm to 0.9nm, 0.5nm to 0.7nm, 0.7nm to 3.5nm, 0.7nm to 2nm , 0.7nm to 0.9nm, 0.9nm to 3.5nm, 0.9nm to 2nm or 2nm to 3.5nm.

In some embodiments, each shell is synthesized in the presence of at least one nanostructured ligand. Ligands can, for example, enhance the miscibility of the nanostructures in solvents or polymers (thus allowing the nanostructures to be distributed throughout the composition so that the nanostructures do not clump together), increase the quantum yield of the nanostructures and/or maintain nanostructures. Structured luminescence (e.g. when incorporating nanostructures into a matrix). In some embodiments, the ligands used for core synthesis and shell synthesis are the same. In some embodiments, the ligands used for core synthesis and those used for shell synthesis are different. After synthesis, any ligands on the surface of the nanostructure can be exchanged with different ligands with other desired properties. Examples of ligands are disclosed in U.S. Patent Nos. 7,572,395, 8,143,703, 8,425,803, 8,563,133, 8,916,064, 9,005,480, 9,139,770, and 9,169,435 and U.S. Patent Application Publication No. 2008/0118755.

Ligands suitable for the synthesis of shells are known to those skilled in the art. In some embodiments, the ligand is a fatty acid selected from the group consisting of lauric acid, caproic acid, myristic acid, palmitic acid, stearic acid, and oleic acid. In some embodiments, the ligand is an organophosphine or organophosphine oxide selected from trioctylphosphine oxide (TOPO), trioctylphosphine (TOP), diphenylphosphine (DPP), triphenylphosphine oxide, and Tributylphosphine oxide. In some embodiments, the ligand is an amine selected from the group consisting of dodecylamine, oleylamine, cetylamine, dioctylamine, and stearylamine. In some embodiments, the ligand is trioctylphosphine oxide, trioctylphosphine, or lauric acid.

In some embodiments, each shell is produced in the presence of a mixture of ligands. In some embodiments, each shell is produced in the presence of a mixture containing 2, 3, 4, 5 or 6 different ligands. In some embodiments, each shell is produced in the presence of a mixture containing 3 different ligands. In some embodiments, the ligand mixture includes tributylphosphine oxide, trioctylphosphine, and lauric acid.

In some embodiments, each shell is produced in the presence of a solvent. In some embodiments, the solvent is selected from 1-octadecene, 1-hexadecene, 1-eicosene, eicosane, octadecane, hexadecane, tetradecane, squalene, squalane, Squalane, trioctylphosphine oxide and dioctyl ether.

In some embodiments, the core, core/buffer, core/shell, or core/buffer/shell and shell precursors are at 20°C to 310°C, 20°C to 280°C, 20°C to 250°C, 20°C to 200°C ℃, 20℃ to 150℃, 20℃ to 100℃, 20℃ to 50℃, 50℃ to 310℃, 50℃ to 280℃, 50℃ to 250℃, 50℃ to 200℃, 50℃ to 150℃, 50℃ to 100℃, 100℃ to 310℃, 100℃ to 280℃, 100℃ to 250℃, 100℃ to 200℃, 100℃ to 150℃, 150℃ to 310℃, 150℃ to 280℃, 150℃ to 250℃, 150℃ to 200℃, 200℃ to 310℃, 200℃ to 280℃, 200℃ to 250℃, 250℃ to 310℃, 250℃ to 280℃ or 280℃ to 310℃. In some embodiments, the core, core/buffer, core/shell, or core/buffer/shell and shell precursors are mixed at a temperature of 20°C to 100°C.

In some embodiments, after mixing the core, core/buffer, core/shell, or core/buffer/shell and shell precursor, the temperature of the reaction mixture is increased to 200°C to 310°C, 200°C to 280°C, Rise from 200℃ to 250℃, 200℃ to 220℃, 220℃ to 310℃, 220℃ to 280℃, 220℃ to 250℃, 250℃ to 310℃, 250℃ to 280℃ or 280℃ to 310℃ temperature. In some embodiments, after contacting the core, core/buffer, core/shell, or core/buffer/shell and shell precursors, the temperature of the reaction mixture is increased to between 250°C and 310°C.

In some embodiments, the time to reach the elevated temperature after mixing the core, core/buffer, core/shell, or core/buffer/shell and shell precursor is 2 to 240 minutes, 2 to 200 minutes, 2 to 100 minutes, 2 to 60 minutes, 2 to 40 minutes, 5 to 240 minutes, 5 to 200 minutes, 5 to 100 minutes, 5 to 60 minutes, 5 to 40 minutes, 10 to 240 minutes, 10 to 200 minutes, 10 to 100 minutes, 10 to 60 minutes, 10 to 40 minutes, 40 to 240 minutes, 40 to 200 minutes, 40 to 100 minutes, 40 to 60 minutes, 60 to 240 minutes, 60 to 200 minutes, 60 to 100 minutes, 100 to 240 minutes, 100 to 200 minutes or 200 to 240 minutes.

In some embodiments, after mixing the core, core/buffer, core/shell, or core/buffer/shell and shell precursor, the temperature of the reaction mixture is maintained at an elevated temperature for 2 to 240 minutes, 2 to 200 minutes, 2 to 100 minutes, 2 to 60 minutes, 2 to 40 minutes, 5 to 240 minutes, 5 to 200 minutes, 5 to 100 minutes, 5 to 60 minutes, 5 to 40 minutes, 10 to 240 minutes, 10 to 200 minutes, 10 to 100 minutes, 10 to 60 minutes, 10 to 40 minutes, 40 to 240 minutes, 40 to 200 minutes, 40 to 100 minutes, 40 to 60 minutes, 60 to 240 minutes, 60 to 200 minutes, 60 to 100 minutes minutes, 100 to 240 minutes, 100 to 200 minutes or 200 to 240 minutes. In some embodiments, the temperature of the reaction mixture is maintained at an elevated temperature for 30 to 120 minutes after mixing the core, core/buffer, core/shell, or core/buffer/shell and shell precursors.

In some embodiments, additional shells are prepared by further addition of shell material precursors which are added to the reaction mixture and then maintained at an elevated temperature. Typically, additional shell precursors are provided after the reaction of the previous shell is substantially complete (eg, when at least one previous precursor is depleted or removed from the reaction or when no additional growth is detected). Further addition of precursors produces additional shells.

In some embodiments, the nanostructure is cooled before adding additional shell material precursors to provide additional shells. In some embodiments, the nanostructures are maintained at an elevated temperature before adding shell material precursors to provide additional shells.

After adding enough shell layers to bring the nanostructure to the desired thickness and diameter, the nanostructure can be cooled. In some embodiments, the core/shell or core/buffer/shell nanostructure is cooled to room temperature. In some embodiments, organic solvent is added to dilute the reaction mixture containing core/shell or core/buffer/shell nanostructures.

In some embodiments, the organic solvent used to dilute the reaction mixture is ethanol, hexane, pentane, toluene, benzene, diethyl ether, acetone, ethyl acetate, dichloromethane (methylene chloride), chloroform, dimethyl methyl formamide or N-methylpyrrolidone. In some embodiments, the organic solvent is toluene.

In some embodiments, core/shell or core/buffer/shell nanostructures are isolated. In some embodiments, core/shell or core/buffer/shell nanostructures are isolated by precipitation using organic solvents. In some embodiments, core/shell or core/buffer/shell nanostructures are isolated by flocculation with ethanol.

The number of monolayers determines the size of the core/shell or core/buffer/shell nanostructure. The dimensions of the core/shell or core/buffer/shell nanostructures can be determined using techniques known to those skilled in the art. In some embodiments, TEM is used to determine the dimensions of core/shell or core/buffer/shell nanostructures.

In some embodiments, the average diameter of the core/shell or core/buffer/shell nanostructure is 1 nm to 15 nm, 1 nm to 10 nm, 1 nm to 9 nm, 1 nm to 8 nm, 1 nm to 7 nm, 1 nm to 6 nm, 1 nm to 5 nm, 5nm to 15nm, 5nm to 10nm, 5nm to 9nm, 5nm to 8nm, 5nm to 7nm, 5nm to 6nm, 6nm to 15nm, 6nm to 10nm, 6nm to 9nm, 6nm to 8nm, 6nm to 7nm, 7nm to 15nm, 7nm to 10nm, 7nm to 9nm, 7nm to 8nm, 8nm to 15nm, 8nm to 10nm, 8nm to 9nm, 9nm to 15nm, 9nm to 10nm or 10nm to 15nm. In some embodiments, the core/shell nanostructures have an average diameter of 6 nm to 7 nm.

Generation of ZnS shell

In some embodiments, the shell deposited on the core, core/buffer/shell or core/shell nanostructure is a ZnS shell.

In some embodiments, the shell precursor contacted with the core, core/buffer/shell or core/shell nanostructure to prepare the ZnS shell includes a zinc source and a sulfur source.

In some embodiments, the ZnS shell passivates defects at the particle surface, which results in increased quantum yield and higher efficiency when used in devices such as LEDs and lasers. Additionally, spectral impurities caused by defect states can be eliminated through passivation, which increases color saturation.

In some embodiments, the zinc source is a dialkyl zinc compound. In some embodiments, the zinc source is zinc carboxylate. In some embodiments, the zinc source is diethyl zinc, dimethyl zinc, zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc carbonate, zinc cyanide, nitric acid Zinc, zinc oleate, zinc oxide, zinc peroxide, zinc perchlorate. Zinc sulfate, zinc caproate, zinc octoate, zinc laurate, zinc myristate, zinc palmitate, zinc stearate, zinc dithiocarbamate or mixtures thereof. In some embodiments, the zinc source is zinc oleate, zinc caproate, zinc octoate, zinc laurate, zinc myristate, zinc palmitate, zinc stearate, zinc dithiocarbamate, or mixtures thereof. In some embodiments, the zinc source is zinc oleate.

In some embodiments, the sulfur source is selected from the group consisting of elemental sulfur, octyl mercaptan, dodecyl mercaptan, octadecanethiol, tributylphosphine sulfide, cyclohexyl isothiocyanate, alpha-toluenethiol, Ethylene trithiocarbonate, allyl mercaptan, bis(trimethylsilyl) sulfide, trioctylphosphine sulfide and mixtures thereof. In some embodiments, the sulfur source is an alkyl-substituted zinc dithiocarbamate. In some embodiments, the sulfur source is octanethiol. In some embodiments, the sulfur source is tributylphosphine sulfide.

In some embodiments, the molar ratio of the core to the zinc source for preparing the ZnS shell is 1:2 to 1:1000, 1:2 to 1:100, 1:2 to 1:50, 1:2 to 1:25, 1:2 to 1:15, 1:2 to 1:10, 1:2 to 1:5, 1:5 to 1:1000, 1:5 to 1:100, 1:5 to 1:50, 1: 5 to 1:25, 1:5 to 1:15, 1:5 to 1:10, 1:10 to 1:1000, 1:10 to 1:100, 1:10 to 1:50, 1:10 to 1:25, 1:10 to 1:15, 1:15 to 1:1000, 1:15 to 1:100, 1:15 to 1:50, 1:15 to 1:25, 1:25 to 1:00 1000, 1:25 to 1:100, 1:25 to 1:50, 1:50 to 1:1000, 1:50 to 1:100 or 1:100 to 1:1000.

In some embodiments, the molar ratio of the core to the sulfur source for preparing the ZnS shell is 1:2 to 1:1000, 1:2 to 1:100, 1:2 to 1:50, 1:2 to 1:25, 1:2 to 1:15, 1:2 to 1:10, 1:2 to 1:5, 1:5 to 1:1000, 1:5 to 1:100, 1:5 to 1:50, 1: 5 to 1:25, 1:5 to 1:15, 1:5 to 1:10, 1:10 to 1:1000, 1:10 to 1:100, 1:10 to 1:50, 1:10 to 1:25, 1:10 to 1:15, 1:15 to 1:1000, 1:15 to 1:100, 1:15 to 1:50, 1:15 to 1:25, 1:25 to 1:00 1000, 1:25 to 1:100, 1:25 to 1:50, 1:50 to 1:1000, 1:50 to 1:100 or 1:100 to 1:1000.

In some embodiments, the number of monolayers in the ZnS shell is 0.25 to 10, 0.25 to 8, 0.25 to 7, 0.25 to 6, 0.25 to 5, 0.25 to 4, 0.25 to 3, 0.25 to 2, 2 to 10, 2 to 8, 2 to 7, 2 to 6, 2 to 5, 2 to 4, 2 to 3, 3 to 10, 3 to 8, 3 to 7, 3 to 6, 3 to 5, 3 to 4, 4 to 10, 4 to 8, 4 to 7, 4 to 6, 4 to 5, 5 to 10, 5 to 8, 5 to 7, 5 to 6, 6 to 10, 6 to 8, 6 to 7, 7 to 10, 7 to 8 or 8 to 10. In some embodiments, the ZnS shell contains 2 to 12 monolayers. In some embodiments, the ZnS shell contains 4 to 6 monolayers.

In some embodiments, the ZnS monolayer has a thickness of about 0.31 nm.

In some embodiments, the ZnS shell has a thickness of 0.08nm to 3.5nm, 0.08nm to 2nm, 0.08nm to 0.9nm, 0.08nm to 0.7nm, 0.08nm to 0.5nm, 0.08nm to 0.2nm, 0.2nm to 3.5 nm, 0.2nm to 2nm, 0.2nm to 0.9nm, 0.2nm to 0.7nm, 0.2nm to 0.5nm, 0.5nm to 3.5nm, 0.5nm to 2nm, 0.5nm to 0.9nm, 0.5nm to 0.7nm, 0.7nm to 3.5nm, 0.7nm to 2nm, 0.7nm to 0.9nm, 0.9nm to 3.5nm, 0.9nm to 2nm or 2nm to 3.5nm.

Indium-doped ZnSe core/shell nanostructures

In some embodiments, the indium-doped ZnSe core/shell nanostructure is an indium-doped ZnSe/ZnS core/shell or an indium-doped ZnSe/ZnSe/ZnS core/buffer/shell nanostructure. In some embodiments, the indium-doped ZnSe core/shell nanostructures are indium-doped ZnSe/ZnSe/ZnS core/buffer/shell quantum dots.

In some embodiments, core/shell nanostructures exhibit high photoluminescence quantum yields. In some embodiments, the indium-doped ZnSe core/shell nanostructure exhibits 30% to 99%, 30% to 95%, 30% to 90%, 30% to 85%, 30% to 80%, 30% to 70%, 30% to 60%, 30% to 50%, 30% to 40%, 40% to 99%, 40% to 95%, 40% to 90%, 40% to 85%, 40% to 80 %, 40% to 70%, 40% to 60%, 40% to 50%, 50% to 99%, 50% to 95%, 50% to 90%, 50% to 85%, 50% to 70%, 50% to 60%, 60% to 99%, 60% to 95%, 60% to 85%, 60% to 80%, 60% to 70%, 70% to 99%, 70% to 95%, 70% to 85%, 70% to 80%, 80% to 99%, 80% to 90%, 80% to 85%, 85% to 99%, 85% to 95%, or 95% to 99% photoluminescence quanta Yield. In some embodiments, indium-doped ZnSe core/shell nanostructures exhibit photoluminescence quantum yields of 50% to 70%. In some embodiments, indium-doped ZnSe core/shell nanostructures exhibit photoluminescence quantum yields of 60% to 70%.

The photoluminescence spectrum of indium-doped ZnSe core/shell nanostructures can cover essentially any desired portion of the spectrum. In some embodiments, the core/shell nanostructure has a photoluminescence spectrum at 300nm and 750nm, 300nm and 650nm, 300nm and 550nm, 300nm and 450nm, 300nm and 400nm, 400nm and 750nm, 400nm and 650nm, 400nm and 550nm, Emission maximum between 400nm and 450nm, 450nm and 750nm, 450nm and 650nm, 450nm and 550nm, 550nm and 750nm, 550nm and 650nm or 650nm and 750nm. In some embodiments, the photoluminescence spectrum of the indium-doped ZnSe core/shell nanostructure has an emission maximum between 400 nm and 500 nm. In some embodiments, the photoluminescence spectrum of the indium-doped ZnSe core/shell nanostructure has an emission maximum between 430 nm and 450 nm.

The size distribution of core/shell nanostructures can be relatively narrow. In some embodiments, the photoluminescence spectrum of the indium-doped ZnSe core/shell nanostructure population can have a photoluminescence spectrum of 10 nm to 60 nm, 10 nm to 40 nm, 10 nm to 30 nm, 10 nm to 20 nm, 20 nm to 60 nm, 20 nm to 40 nm, 20 nm to Full width at half maximum of 30nm, 30nm to 60nm, 30nm to 40nm or 40nm to 60nm. In some embodiments, the photoluminescence spectrum of the indium-doped ZnSe core/shell nanostructure population may have a full width at half maximum of 20 nm to 30 nm.

The resulting indium-doped ZnSe core/shell nanostructures are optionally embedded in a matrix (e.g., organic polymer, silicon-containing polymer, inorganic, glassy, and/or other matrix) for generating nanostructured phosphors and /or incorporated into devices such as LEDs, backlights, downlights or other display or lighting units or optical filters. Exemplary phosphors and illumination units can produce a specific color of light, for example, by combining a population of nanostructures with an emission maximum at or near a desired wavelength or by combining two or more different populations of nanostructures with different emission maxima. to produce a wide color gamut. A variety of suitable matrices are known in the art. See, for example, U.S. Patent No. 7,068,898 and U.S. Patent Application Publication Nos. 2010/0276638, 2007/0034833, and 2012/0113672. Exemplary nanostructured phosphor films, LEDs, backlight units, and the like are described, for example, in U.S. Patent Application Publication Nos. 2010/0276638, 2012/0113672, 2008/0237540, 2010/0110728, and 2010/0155749, and U.S. Patent Nos. 7,374,807, 7,645,397, 6,501,091 and 6,803,719.

Indium-doped ZnSe core/shell nanostructures obtained by these methods are also features of the present invention. Accordingly, one class of embodiments provides a population of indium-doped ZnSe core/shell nanostructures. In some embodiments, the indium-doped ZnSe core/shell nanostructures are quantum dots.

Nanostructured layer

In some embodiments, the present disclosure provides a nanostructure layer comprising at least one population of nanostructures, wherein the nanostructures comprise an indium-doped ZnSe core and at least one shell, wherein at least one shell comprises ZnS.

In some embodiments, the nanostructure has a FWHM of about 15 to about 30.

In some embodiments, the nanostructures are quantum dots.

molded products

In some embodiments, the present disclosure provides molded articles comprising at least one population of nanostructures, wherein the nanostructures comprise an indium-doped ZnSe core and at least one shell, wherein at least one shell comprises ZnS.

In some embodiments, the nanostructure has a FWHM of about 15 to about 30.

In some embodiments, the molded article is a film, a substrate of a display, or a light emitting diode.

In some embodiments, the nanostructures are quantum dots.

In some embodiments, the present invention provides a light-emitting diode, including:

(a) Anode;

(b) cathode; and

(c) A luminescent layer between the anode and the cathode, wherein the luminescent layer comprises a nanostructure comprising an indium-doped ZnSe core and at least one shell, wherein at least one shell comprises ZnS.

In some embodiments, the light emitting diode further includes a hole transport layer. In some embodiments, the hole transport layer includes a material selected from the group consisting of amines, triarylamines, thiophenes, carbazoles, phthalocyanines, porphyrins, and combinations thereof. In some embodiments, the hole transport layer includes N,N'-bis(naphth-1-yl)-N,N'-bis(4-vinylphenyl)-4,4'-diamine.

In some embodiments, the light emitting diode further includes an electron transport layer. In some embodiments, the electron transport layer comprises imidazole, pyridine, pyrimidine, pyridazine, pyrazine, oxadiazole, quinoline, quinoxaline, anthracene, benzanthracene, pyrene, perylene, benzimidazole, tris Materials of azines, ketones, phosphine oxides, phenazines, phenanthrolines, triarylboranes, metal oxides and combinations thereof. In some embodiments, the electron transport layer includes 1,3-bis(3,5-dipyridin-3-ylphenyl)benzene (B3PyPB), bathocuproline, bathophenanthroline, 3-(biphenyl-4 -base)-5-(4-tert-butyl)-butylphenyl)-4-phenyl-4H-1,2,4-triazole, 2-(4-biphenyl)-5-phenyl -1,3,4-oxadiazole, 3,5-bis(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole, bis(8-hydroxy-2- Methylquinoline)-(4-phenylphenoxy)aluminum, 2,5-bis(1-naphthyl)-1,3,4-oxadiazole, 3,5-diphenyl-4-( 1-naphthyl)-1H-1,2,4-triazole, 1,3,5-tris(m-pyridin-3-ylphenyl)benzene (TmPyPB), 2,2',2”-(1 ,3,5-phenyltriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi), tris-(8-hydroxyquinoline)aluminum, TiO ₂ , ZnO, SnO ₂ , SiO ₂ , ZrO ₂ or ZnMgO. In some embodiments, the electron transport layer includes ZnMgO.

Preparation of nanostructured layers

In some embodiments, the nanostructured layer can be embedded in a polymer matrix. As used herein, the term "embedded" is used to mean that a population of nanostructures is surrounded or encapsulated by a polymer that constitutes a majority component of the matrix. In some embodiments, at least one population of nanostructures is suitably evenly distributed throughout the matrix. In some embodiments, at least one population of nanostructures is distributed according to an application-specific distribution. In some embodiments, the nanostructures are mixed in the polymer and applied to the surface of the substrate.

In some embodiments, the nanostructured composition is deposited to form a nanostructured layer. In some embodiments, the nanostructured composition may be deposited by any suitable method known in the art, including, but not limited to, brushing, spraying, solvent spray, wet coating, adhesive coating, spin coating, tape coating ( tape-coating), roller coating, flow coating, inkjet vapor spraying, drop casting, blade coating, mist deposition or combinations thereof. The nanostructured composition can be coated directly on the desired substrate layer. Alternatively, the nanostructured composition can be formed as a separate element into a solid layer and then applied to a substrate. In some embodiments, the nanostructured composition can be deposited on one or more barrier layers.

In some embodiments, the nanostructured layer is solidified after deposition. Suitable curing methods include light curing such as UV curing and thermal curing. Traditional laminate film processing methods, tape coating methods, and/or roll-to-roll manufacturing methods can be used to form the nanostructured layer.

spin coating

In some embodiments, the nanostructured composition is deposited onto the substrate using spin coating. In spin coating, a small amount of material is typically deposited on the center of a substrate loaded onto a machine called a spinner, which is held in place by a vacuum. High-speed rotation is exerted on the substrate by a spinner, which results in centripetal force to spread the material from the center to the edges of the substrate. Although most of the material is thrown off, a certain amount remains on the substrate, continuing to form a film of material on the surface as the rotation proceeds. In addition to the parameters selected for the spin process (such as spin speed, acceleration, and spin time), the final thickness of the film is determined by the properties of the deposited material and the substrate. In some embodiments, a rotation speed of 1500 to 6000 rpm is used, with a rotation time of 10-60 seconds.

mist deposit

In some embodiments, the nanostructured composition is deposited onto the substrate using mist deposition. Mist deposition occurs at room temperature and atmospheric pressure and allows precise control of film thickness by varying process conditions. During mist deposition, the liquid source material is reduced to a very fine mist and transported to the deposition chamber by nitrogen gas. The mist is then attracted to the wafer surface by a high voltage potential between the field screen and the wafer holder. Once the droplets coalesce on the wafer surface, the wafer is removed from the chamber and thermally cured to allow the solvent to evaporate. A liquid precursor is a mixture of solvent and material to be deposited. It is delivered to the atomizer via pressurized nitrogen. Price, S.C., et al., "Formation of Ultra-Thin Quantum Dot Films by Mist Deposition," ESC Transactions 11: 89-94 (2007).

Spray

In some embodiments, the nanostructured composition is deposited onto a substrate using spray coating. Typical equipment used for spray coating includes nozzles, atomizers, precursor solutions, and carrier gases. During spray deposition, the precursor solution is pulverized into micron-sized droplets with the aid of a carrier gas or by atomization (e.g., ultrasonic, air blast, or electrostatic). The droplets emerging from the atomizer are accelerated through the nozzle across the substrate surface with the help of a carrier gas that is controlled and adjusted as needed. The relative motion between the nozzle and the substrate is defined by design with the goal of complete coverage of the substrate.

In some embodiments, application of the nanostructured composition also includes a solvent. In some embodiments, the solvent used to apply the nanostructured composition is water, an organic solvent, an inorganic solvent, a halogenated organic solvent, or mixtures thereof. Exemplary solvents include, but are not limited to, water, _D2O , acetone, ethanol, dioxane, ethyl acetate, methyl ethyl ketone, isopropyl alcohol, anisole, gamma-butyrolactone, dimethylformamide , N-methylpyrrolidone, dimethylacetamide, hexamethylphosphoramide, toluene, dimethyl sulfoxide, cyclopentanone. Tetramethylene sulfoxide, xylene, ε-caprolactone, tetrahydrofuran, tetrachloroethylene, chloroform, chlorobenzene, methylene chloride, 1,2-dichloroethane, 1,1,2,2-tetrachloro Ethane or mixtures thereof.

In some embodiments, the nanostructured composition is thermally cured to form a nanostructured layer. In some embodiments, the composition is cured using UV light. In some embodiments, the nanostructured composition is coated directly on the barrier layer of the nanostructured film, and an additional barrier layer is subsequently deposited on the nanostructured layer to create the nanostructured film. A support substrate can be used underneath the barrier film to add strength, stability, and coating uniformity, and to prevent material inconsistencies, bubble formation, and wrinkling or folding of the barrier material or other materials. Additionally, one or more barrier layers are preferably deposited on the nanostructured layer to seal the material between the top and bottom barrier layers. Suitably, the barrier layer can be deposited as a laminate film and optionally sealed or further processed before incorporating the nanostructured film into a specific lighting device. As one of ordinary skill in the art will appreciate, the nanostructure composition deposition process may include additional or varying components. These embodiments will allow for in-line process tuning of nanostructure emission properties, such as brightness and color (e.g., tuning the quantum dot film white point), as well as nanostructure film thickness and other properties. Additionally, these embodiments allow for regular testing of nanostructured film properties during production, as well as any necessary switching to achieve precise nanostructured film properties. This testing and adjustment can also be accomplished without changing the mechanical configuration of the process line, since a computer program can be employed to electronically vary the corresponding amounts of mixture used to form the nanostructured film.

barrier layer

In some embodiments, the molded article includes one or more barrier layers disposed on one or both sides of the nanostructured layer. Suitable barrier layers protect the nanostructured layer and molded article from environmental conditions such as high temperature, oxygen and moisture. Suitable barrier materials include non-yellowing transparent optical materials that are hydrophobic, chemically and mechanically compatible with the molded article, exhibit photostability and chemical stability, and can withstand high temperatures. In some embodiments, the one or more barrier layers are index matched to the molded article. In some embodiments, the matrix material of the molded article and one or more adjacent barrier layers are index matched to have similar refractive indices such that most of the light transmitted through the barrier layer towards the molded article is transmitted from the barrier layer into the nanostructured layer. This index matching reduces light loss at the interface between the barrier layer and the matrix material.

The barrier layer is suitably a solid material and may be a solidified liquid, gel or polymer. Depending on the specific application, the barrier layer may include flexible or non-flexible materials. The barrier layer is preferably a planar layer and may include any suitable shape and surface area configuration, depending on the particular lighting application. In some embodiments, the one or more barrier layers are compatible with laminate film processing techniques such that the nanostructured layer is disposed on at least a first barrier layer, and according to one embodiment at least a second barrier layer is located opposite the nanostructured layer. The sides are disposed on the nanostructured layer to form a molded article. Suitable barrier materials include any suitable barrier material known in the art. In some embodiments, suitable barrier materials include glasses, polymers, and oxides. Suitable barrier materials include, but are not limited to, polymers such as polyethylene terephthalate (PET); oxides such as silicon oxide, titanium oxide, or aluminum oxide (e.g., SiO ₂ , Si ₂ O ₃ , TiO ₂ or Al ₂ O ₃ ); and suitable combinations thereof. Preferably, each barrier layer of the molded article includes at least 2 layers containing different materials or compositions such that the multi-layer barrier eliminates or reduces pinhole defect alignment in the barrier layer, thereby providing oxygen and moisture penetration into the nanostructure. Effective barrier. The nanostructured layer may include any suitable material or combination of materials and any suitable number of barrier layers on either or both sides of the nanostructured layer. The material, thickness, and number of barrier layers will depend on the specific application and will be appropriately selected to maximize barrier protection and brightness of the nanostructured layer while minimizing the thickness of the molded article. In preferred embodiments, each barrier layer includes a laminated film, preferably a dual laminated film, wherein the thickness of each barrier layer is sufficiently thick to eliminate wrinkling during roll-to-roll or laminate manufacturing processes. In embodiments where the nanostructures contain heavy metals or other toxic materials, the number or thickness of the barriers may further depend on legal toxicity guidance, which may require more or thicker barrier layers. Other considerations for barriers include cost, availability, and mechanical strength.

In some embodiments, the nanostructured film includes two or more barrier layers adjacent each side of the nanostructured layer, e.g., two or three layers on each side of the nanostructured layer or of the nanostructured layer. Two barrier layers on each side. In some embodiments, each barrier layer includes a thin glass plate, such as a glass plate having a thickness of about 100 μm, 100 μm or less, or 50 μm or less.

Each barrier layer of the molded article may have any suitable thickness, depending on the specific requirements and characteristics of the lighting device and application, as well as the individual film components, such as barrier layers and nanostructured layers, as one of ordinary skill in the art will understand. In some embodiments, each barrier layer may have a thickness of 50 μm or less, 40 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, or 15 μm or less. In certain embodiments, the barrier layer includes an oxide coating, which may include materials such as silicon oxide, titanium oxide, and aluminum oxide (eg, SiO ₂ , Si ₂ O ₃ , TiO _{2 ,} or Al ₂ O ₃ ). The oxide coating may have a thickness of about 10 μm or less, 5 μm or less, 1 μm or less, or 100 nm or less. In certain embodiments, the barrier layer includes a thin oxide coating having a thickness of about 100 nm or less, 10 nm or less, 5 nm or less, or 3 nm or less. The top and/or bottom barrier may consist of a thin oxide coating, or may include a thin oxide coating and one or more additional material layers.

Nanostructured Layer Characteristics and Implementations

In some embodiments, nanostructured layers are used to form display devices. As used herein, a display device refers to any system with an illuminated display. These devices include, but are not limited to, liquid crystal displays (LCDs), televisions, computers, mobile phones, smart phones, personal digital assistants (PDAs), gaming devices, electronic reading devices, digital cameras, etc.

Molded articles with improved properties

In some embodiments, molded articles prepared using nanostructures exhibit about 1.5% to about 20%, about 1.5% to about 15%, about 1.5% to about 12%, about 1.5% to about 10%, about 1.5% to about 8%, about 1.5% to about 4%, about 1.5% to about 3%, about 3% to about 20%, about 3% to about 15%, about 3% to about 12%, about 3% to about 10%, about 3% to about 8%, about 8% to about 20%, about 8% to about 15%, about 8% to about 12%, about 8% to about 10%, about 10% about 20%, An EQE of about 10% to about 15%, about 10% to about 12%, about 12% to about 20%, about 12% to about 15%, or about 15% to about 20%. In some embodiments, the nanostructures are quantum dots. In some embodiments, the molded article is a light emitting diode.

In some embodiments, molded articles prepared using nanostructures exhibit a photoluminescence spectrum with an emission maximum between 400 nm and 500 nm. In some embodiments, molded articles prepared using nanostructures exhibit a photoluminescence spectrum with an emission maximum between 430 nm and 450 nm.

The following examples are illustrative, but not limiting, of the products and methods described herein. Appropriate modifications and adaptations of various conditions, formulations and other parameters commonly used in the art and which will be apparent to those skilled in the art based on this disclosure are within the spirit and scope of the invention.

Example

Example 1

Synthesis of InCl ₃ -doped ZnSe nanostructures

Oleylamine (15 mL) was added to a 100 mL three-neck flask and vacuum degassed at 110°C for 30 minutes. The mixture was heated to 300°C under a stream of nitrogen. At this temperature, 1.5 mL of a solution of trioctylphosphine selenide (TOPSe, 1.92 M) and diphenylphosphine (225 μL) in trioctylphosphine (TOP, 1.0 mL total) was added to the flask. Once the temperature rebounded to 300°C, rapidly inject a solution of diethylzinc (295 μL) in TOP (2.5 mL) and indium chloride (8 mg, 36 μmol) in TOP (2.5 mL). The temperature was set at 280°C and after 5 minutes a solution of diethylzinc (1.38 mL) and 10.5 mL TOPSe (1.92 M) in TOP (total 6.5 mL) was introduced at a rate of 1 mL/min. Stop for 10 minutes after 7.5mL and stop for 15 minutes after 9.5mL. Additional oleylamine (20 mL) was infused at a rate of 1.5 mL/min starting 26 minutes after zinc infusion. After the infusion is complete, the reaction mixture is held at 280°C for 15 minutes and then cooled to room temperature. The growth solution was then diluted with an equal volume of toluene (65 mL) and the nanocrystals were precipitated by adding ethanol (130 mL). After centrifugation, the supernatant was discarded and the nanocrystals were redispersed in hexane (40 mL). Concentration was measured by evaporating the solvent from an aliquot as dry weight.

Example 2

Synthesis of InCl ₃ -doped ZnSe/ZnSe/ZnS core/buffer layer/shell nanostructures

Use the following procedure to coat a ZnSe/ZnS buffer layer/shell on an _InCl doped ZnSe nanocrystal core with an average diameter of 4.0 nm with 4 ML ZnSe buffer layer and 6 ML ZnS.

Add zinc oleate (6.03g), lauric acid (3.85g) and trioctylphosphine oxide (4.93g) to a 100mL three-neck flask. After three cycles of vacuum and nitrogen backfill, TOP (9.9 mL) and InCl3 _- doped ZnSe core solution (1.5 mL, 78.9 mg/mL in toluene) were added to the flask. The solution was degassed under vacuum at 100°C for 20 minutes and then heated to 310°C under a stream of nitrogen. 10 minutes after reaching this temperature, start a slow infusion of TOPSe (9.5 mL, 0.3 M in TOP) at a rate of 0.19 mL/min. After the selenium infusion was completed, the reaction was held at 310°C for 10 minutes. An infusion of tributylphosphine sulfide (16.9 mL, 0.4 M in TOP) was then started at a rate of 0.42 mL/minute. After the sulfur infusion was complete, the reaction was held at 310°C for 10 minutes and then cooled to room temperature. The reaction mixture was diluted with toluene (50 mL). The core/buffer/shell nanocrystals were precipitated by adding ethanol (100 mL), then separated by centrifugation, the supernatant was decanted, and the nanocrystals were redispersed in hexanes (50 mL). The precipitation was repeated once with ethanol (50 mL) and finally the nanocrystals were redispersed in octane (7 mL). The solution was filtered through a polytetrafluoroethylene (PTFE) 0.22 μm syringe filter and the concentration was adjusted to 18 mg/mL after measuring the dry weight of the aliquots.

Example 3

Synthesis of Indium-Doped ZnSe Nanostructures

Indium-doped ZnSe nanostructures can be prepared using various indium salts using the procedures in Examples 1-2. The amounts of indium doped ZnSe/ZnS core/shell nanostructures and the resulting optical properties are provided in Table 1.

Table 1

As shown in Table 1 and Figure 1, the PWL of indium-doped ZnSe core and ZnSe/ZnSe/ZnS core/buffer/shell nanostructures can be tuned by changing the amount and type of indium salt used.

Example 4

Analysis of electroluminescent devices fabricated using nanostructures

Devices were prepared by a combination of spin coating and thermal evaporation. First, the hole injection material poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) (50 nm) was spin-coated on UV-ozone-treated indium tin oxide ( ITO) substrate and baked at 200°C for 15 minutes. Transfer the device to an inert atmosphere and add the hole transport material N,N'-bis(naphth-1-yl)-N,N'-bis(4-vinylphenyl)biphenyl-4,4' - Diamine (VNPB) (20 nm) was deposited by spin coating and baked at 200°C for 15 minutes. A solution of ZnSe/ZnS or indium-doped ZnSe/ZnS quantum dots was deposited by spin coating, followed by spin coating of the electron transport material ZnMgO (20 nm). An Al cathode (150 nm) was then deposited by thermal evaporation, followed by encapsulation of the device using cover-glass, getter and epoxy.

Figure 5 shows the lifetime curve of a light-emitting device prepared using undoped ZnSe/ZnS quantum dots compared to a light-emitting device prepared using indium-doped ZnSe/ZnSe/ZnS core/buffer layer/shell quantum dots. As shown in Figure 5 and Table 2, devices prepared using indium-doped ZnSe/ZnSe/ZnS core/buffer/shell quantum dots showed longer operation than devices prepared using undoped ZnSe/ZnS quantum dots. life.

Table 2

Material T ₉₅ (s) T ₅₀ (s) EQE(%) Undoped ZnSe/ZnS 0.4 9.1 3.5 InCl ₃ doped (0.0270%In)ZnSe/ZnSe/ZnS 1.8 29.5 2.3

Now that the invention has been fully described, it will be understood by those of ordinary skill in the art that it may equally be practiced within a wide and equivalent range of conditions, formulations and other parameters without affecting the scope of the invention or any embodiments thereof. All patents, patent applications, and publications cited herein are incorporated by reference in their entirety.

Claims (73)

1. A nanostructure comprising a core surrounded by at least one shell, wherein the core consists of ZnSe and an indium dopant, wherein the at least one shell contains ZnS, and wherein the nanostructure has an emission wavelength at 435 nm and 500nm. 2. The nanostructure of claim 1, wherein the nanostructure has an emission wavelength between 440 nm and 480 nm. 3. The nanostructure of claim 1, wherein the nanostructure has an emission wavelength between 440 nm and 460 nm. 4. The nanostructure of claim 1, wherein said core is surrounded by a shell. 5. The nanostructure of claim 1, wherein at least one shell contains 3-8 ZnS monolayers. 6. The nanostructure of claim 1, wherein at least one shell contains 6 ZnS monolayers. 7. The nanostructure of claim 1, wherein said nanostructure further comprises a buffer layer between said core and said at least one shell. 8. The nanostructure of claim 7, wherein the buffer layer contains ZnSe. 9. The nanostructure of claim 8, wherein the buffer layer contains 2-6 ZnSe monolayers. 10. The nanostructure of claim 8, wherein the buffer layer contains 4 ZnSe monolayers. 11. The nanostructure of claim 1, wherein the nanostructure has a photoluminescence quantum yield between 50% and 90%. 12. The nanostructure of claim 1, wherein the nanostructure has a photoluminescence quantum yield between 60% and 90%. 13. The nanostructure of claim 1, wherein the nanostructure has a FWHM between 10 nm and 40 nm. 14. The nanostructure of claim 1, wherein the nanostructure has a FWHM between 10 nm and 30 nm. 15. The nanostructure of claim 1, wherein the nanostructure comprises a buffer layer containing 2-6 ZnSe monolayers and at least one shell containing 3-8 ZnS monolayers. 16. The nanostructure of claim 1, wherein said nanostructure is a quantum dot. 17. The nanostructure of claim 1, wherein the nanostructure does not contain cadmium. 18. A device comprising the nanostructure of any one of claims 1-17. 19. A method for preparing nanocrystal cores, comprising: (a) mixing a source of selenium and at least one ligand to produce a reaction mixture; and (b) contacting the reaction mixture obtained in (a) with a zinc source and at least one indium salt; to provide a nanocrystalline core composed of ZnSe and indium dopants. 20. The method of claim 19, wherein the selenium source in (a) is selected from the group consisting of trioctylphosphine selenide, tris(n-butyl)phosphine selenide, tris(sec-butyl)phosphine selenide, tri(sec-butyl)phosphine selenide, Tert-butyl)phosphine selenide, trimethylphosphine selenide, triphenylphosphine selenide, diphenylphosphine selenide, phenylphosphine selenide, cyclohexylphosphine selenide, octaselenol, dodedeselenol, Selenophenol, elemental selenium, hydrogen selenide, bis(trimethylsilyl)selenide and mixtures thereof. 21. The method of claim 19, wherein the selenium source in (a) is trioctylphosphine selenide. 22. The method of claim 19, wherein said at least one ligand in (a) is selected from trioctylphosphine oxide, trioctylphosphine, diphenylphosphine, triphenylphosphine oxide and tributylphosphine oxide phosphine. 23. The method of claim 19, wherein said at least one ligand in (a) is trioctylphosphine. 24. The method of claim 19, wherein the zinc source in (b) is selected from the group consisting of diethyl zinc, dimethyl zinc, zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, Zinc fluoride, zinc carbonate, zinc cyanide, zinc nitrate, zinc oxide, zinc peroxide, zinc perchlorate and zinc sulfate. 25. The method of claim 19, wherein the zinc source in (b) is diethyl zinc. 26. The method of claim 19, wherein the indium salt in (b) is selected from the group consisting of indium bromide, indium chloride, indium fluoride, indium iodide, indium nitrate, indium perchlorate, indium hydroxide, acetic acid Indium and its mixtures. 27. The method of claim 19, wherein the indium salt in (b) is selected from the group consisting of indium bromide, indium chloride or indium acetate. 28. The method of claim 19, wherein the indium salt in (b) is indium chloride. 29. The method of claim 19, wherein the indium salt in (b) is indium acetate. 30. The method of claim 19, further comprising: (c) Contacting the reaction mixture in (b) with a zinc source and a selenium source. 31. The method of claim 30, wherein the zinc source in (c) is selected from the group consisting of diethyl zinc, dimethyl zinc, zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, Zinc fluoride, zinc carbonate, zinc cyanide, zinc nitrate, zinc oxide, zinc peroxide, zinc perchlorate and zinc sulfate. 32. The method of claim 30, wherein said zinc source in (c) is diethyl zinc. 33. The method of claim 30, wherein the selenium source in (c) is selected from trioctylphosphine selenide, tris(n-butyl)phosphine selenide, tris(sec-butyl)phosphine selenide, tri(sec-butyl)phosphine selenide, Tert-butyl)phosphine selenide, trimethylphosphine selenide, triphenylphosphine selenide, diphenylphosphine selenide, phenylphosphine selenide, cyclohexylphosphine selenide, octaselenol, dodedeselenol, Selenophenol, elemental selenium, hydrogen selenide, bis(trimethylsilyl)selenide and mixtures thereof. 34. The method of claim 30, wherein the selenium source in (c) is trioctylphosphine selenide. 35. The method of claim 19, wherein said mixing in (a) is performed at a temperature of 250°C to 350°C. 36. The method of claim 19, wherein said mixing in (a) is performed at a temperature of 300°C. 37. The method of claim 19, wherein said contacting in (b) is performed at a temperature of 250°C to 350°C. 38. The method of claim 19, wherein said contacting in (b) is performed at a temperature of 300°C. 39. The method of claim 19, wherein said contacting in (b) further comprises at least one ligand. 40. The method of claim 30, wherein said contacting in (c) is performed at a temperature of 250°C to 350°C. 41. The method of claim 30, wherein said contacting in (c) is performed at a temperature of 300°C. 42. The method of claim 30, wherein said contacting in (c) further comprises at least one ligand. 43. The method of claim 42, wherein said at least one ligand is trioctylphosphine or diphenylphosphine. 44. The method of claim 19, wherein the selenium source in (a) is trioctylphosphine selenide, the zinc source in (b) is diethylzinc, and the selenium source in (b) Indium salt is indium chloride. 45. The method of claim 31, wherein the selenium source in (a) and (c) is trioctylphosphine selenide and the zinc source in (b) and (c) is diethylzinc, and the indium salt in (b) is indium chloride. 46. A method of producing a nanostructure comprising a core and at least one shell, comprising: (d) mixing nanocrystals prepared by the method of any one of claims 19-45 with a solution containing a zinc source and a sulfur source; and (e) optionally repeat (d); to produce a nanostructure comprising a core and at least one shell. 47. The method of claim 46, wherein said mixing in (d) is performed at a temperature of 20°C to 310°C. 48. The method of claim 46, wherein said mixing in (d) is performed at a temperature of 20°C to 100°C. 49. The method of claim 46, wherein the zinc source of (d) is selected from the group consisting of diethyl zinc, dimethyl zinc, zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, fluorine Zinc chloride, zinc carbonate, zinc cyanide, zinc nitrate, zinc oleate, zinc oxide, zinc peroxide, zinc perchlorate, zinc sulfate, zinc caproate, zinc octoate, zinc laurate, zinc myristate, palmitic acid Zinc, zinc stearate, zinc dithiocarbamate or mixtures thereof. 50. The method of claim 46, wherein the sulfur source of (d) is selected from the group consisting of elemental sulfur, octyl mercaptan, dodecyl mercaptan, octadecane mercaptan, tributylphosphine sulfide, isothiocyanate Cyclohexyl ester, α-toluenethiol, ethylene trithiocarbonate, allyl mercaptan, bis(trimethylsilyl) sulfide, trioctylphosphine sulfide and mixtures thereof. 51. A method of preparing a nanostructure comprising a core, a buffer layer and at least one shell, the method comprising: (d) mixing nanocrystals prepared by the method of any one of claims 19-45 with a solution containing a zinc source and a selenium source; (e) optionally repeat (d); (f) mixing the reaction mixture of (e) with a solution containing a zinc source and a sulfur source; and (g) optionally repeat (f); To produce a nanostructure including a core, a buffer layer and at least one shell. 52. The method of claim 51, wherein said mixing in (d) is performed at a temperature of 20°C to 310°C. 53. The method of claim 51, wherein said mixing in (d) is performed at a temperature of 20°C to 100°C. 54. The method of claim 51, wherein the zinc source of (d) is selected from the group consisting of diethyl zinc, dimethyl zinc, zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, fluorine Zinc chloride, zinc carbonate, zinc cyanide, zinc nitrate, zinc oleate, zinc oxide, zinc peroxide, zinc perchlorate, zinc sulfate, zinc caproate, zinc octoate, zinc laurate, zinc myristate, palmitic acid Zinc, zinc stearate, zinc dithiocarbamate or mixtures thereof. 55. The method of claim 51, wherein the selenium source of (d) is selected from trioctylphosphine selenide, tris(n-butyl)phosphine selenide, tris(sec-butyl)phosphine selenide, tris(tert. Butyl)phosphine selenide, trimethylphosphine selenide, triphenylphosphine selenide, diphenylphosphine selenide, phenylphosphine selenide, cyclohexylphosphine selenide, octaselenol, dodeceselenol, selenium Phenol, elemental selenium, hydrogen selenide, bis(trimethylsilyl)selenide and mixtures thereof. 56. The method of claim 51, wherein the zinc source of (f) is selected from the group consisting of diethyl zinc, dimethyl zinc, zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, fluorine Zinc chloride, zinc carbonate, zinc cyanide, zinc nitrate, zinc oleate, zinc oxide, zinc peroxide, zinc perchlorate, zinc sulfate, zinc caproate, zinc octoate, zinc laurate, zinc myristate, palmitic acid Zinc, zinc stearate, zinc dithiocarbamate or mixtures thereof. 57. The method of claim 51, wherein the sulfur source of (f) is selected from the group consisting of elemental sulfur, octyl mercaptan, dodecyl mercaptan, octadecane mercaptan, tributylphosphine sulfide, isothiocyanate Cyclohexyl ester, α-toluenethiol, ethylene trithiocarbonate, allyl mercaptan, bis(trimethylsilyl) sulfide, trioctylphosphine sulfide and mixtures thereof. 58. The method of claim 51, wherein the contacting in (f) is carried out at a temperature of 200°C to 350°C. 59. The method of claim 51, wherein the contacting in (f) is performed at a temperature of 310°C. 60. The method of claim 51, wherein said mixing in (d) further comprises at least one ligand. 61. The method of claim 60, wherein the at least one ligand is selected from trioctylphosphine oxide, trioctylphosphine, diphenylphosphine, triphenylphosphine oxide and tributylphosphine oxide. 62. The method of claim 61, wherein said at least one ligand is trioctylphosphine or trioctylphosphine oxide. 63. The method of claim 51, wherein said mixture in (f) further comprises at least one ligand. 64. The method of claim 63, wherein the at least one ligand is selected from trioctylphosphine oxide, trioctylphosphine, diphenylphosphine, triphenylphosphine oxide and tributylphosphine oxide. 65. The method of claim 63, wherein said at least one ligand is trioctylphosphine or trioctylphosphine oxide. 66. A light-emitting diode, comprising: (a) Anode; (b) cathode; and (c) A light-emitting layer comprising the nanostructure of any one of claims 1-17. 67. The light emitting diode of claim 66, further comprising a hole transport layer. 68. The light emitting diode of claim 66, further comprising an electron transport layer. 69. The light emitting diode of claim 67, wherein the hole transport layer comprises a material selected from the group consisting of amines, triarylamines, thiophenes, carbazoles, phthalocyanines, porphyrins, and combinations thereof. 70. The light emitting diode of claim 67, wherein the hole transport layer comprises N,N'-bis(naphth-1-yl)-N,N'-bis(4-vinylphenyl)-4 ,4'-diamine. 71. The light emitting diode of claim 68, wherein the electron transport layer comprises a compound selected from the group consisting of imidazole, pyridine, pyrimidine, pyridazine, pyrazine, oxadiazole, quinoline, quinoxaline, anthracene, benzanthracene, Materials of pyrene, perylene, benzimidazole, triazine, ketone, phosphine oxide, phenazine, phenanthroline, triarylborane, metal oxides and combinations thereof. 72. The light-emitting diode of claim 68, wherein the electron transport layer comprises 1,3-bis(3,5-dipyridin-3-ylphenyl)benzene (B3PyPB), bathocuproline, and biphenanthroline Phinoline, 3-(biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole, 2-(4-biphenyl) -5-phenyl-1,3,4-oxadiazole, 3,5-bis(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole, bis(8 -Hydroxy-2-methylquinoline)-(4-phenylphenoxy)aluminum, 2,5-bis(1-naphthyl)-1,3,4-oxadiazole, 3,5-diphenyl Base-4-(1-naphthyl)-1H-1,2,4-triazole, 1,3,5-tris(m-pyridin-3-ylphenyl)benzene (TmPyPB), 2,2', 2”-(1,3,5-phenyltriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi), tris-(8-hydroxyquinoline)aluminum, TiO ₂ , ZnO, SnO ₂ , SiO ₂ , ZrO ₂ or ZnMgO. 73. The light emitting diode of claim 68, wherein the electron transport layer comprises ZnMgO.